What was the Ark of the Covenant, and was it real?

The Ark of the Covenant was definitely real and was a part of the tabernacle, being placed in the Holy of Holies behind the curtain. I will include articles below from three Bible Dictionaries that will give you some information. It will be basically the same information, but each might add something more to help you. Your best source for concise information is in Bible Encyclopedias and Dictionaries. Some people believe the Ark is existence today, though hidden.

From the New Bible Dictionary:

ARK OF THE COVENANT. Called also 'ark of the Lord', 'ark of God', 'ark of the covenant of the Lord' (Dt. 10:8) and 'ark of the testimony' (edut = covenant-terms: *Witness). The ark was a rectangular box ('aron) made of acacia wood, and measured 2 1/2 x 1 1/2 x 1 1/2 cubits (i.e. c. 4 x 2 1/2 x 2 1/2 feet or c. 1.22 m x 76 cm x 76 cm). The whole was covered with gold and was carried on poles inserted in rings at the four lower corners. The lid, or 'mercy-seat', was a gold plate surrounded by two antithetically placed cherubs with outspread wings.

The ark served (i) as receptacle for the two tablets of the Decalogue (Ex. 25:16, 21; 40:20; Dt. 10:1-5) and also for the pot of manna and Aaron's rod (Heb. 9:4-5); (ii) as the meeting-place in the inner sanctuary where the Lord revealed his will to his servants (Moses: Ex. 25:22; 30:36; Aaron: Lv. 16:2; Joshua: Jos. 7:6). Thus it served as the symbol of the divine presence guiding his people. The ark was made at Sinai by Bezalel to the pattern given to Moses (Ex. 25:8ff.). It was used as a depository for the written law (Dt. 31:9; Jos. 24:26) and played a significant part at the crossing of Jordan (Jos. 3-4), the fall of Jericho (Jos. 6) and the ceremony of remembering the covenant at Mt Ebal (Jos. 8:30ff.).

From Gilgal the ark was moved to Bethel (Jdg. 2:1; 20:27), but was taken to Shiloh in the time of the Judges (1 Sa. 1:3; 3:3), remaining there till captured by the Philistines on the battlefield at Ebenezer (1 Sa. 4). Because its presence caused 7 months of plagues, the Philistines returned it to Kiriath-jearim, where it remained for 20 years (1 Sa. 5:1-7:2), except possibly for a temporary move to Saul's camp near Beth-aven (1 Sa. 14:18where, however, lxx indicates that the original reading was probably 'ephod').

David installed the ark in a tent at Jerusalem (2 Sa. 6), and would not remove it during Absalom's rebellion (2 Sa. 15:24-29). It was placed in the Temple with great ceremony in the reign of Solomon (1 Ki. 8:1ff.), and re-sited in the sanctuary during Josiah's reforms (2 Ch. 35:3) when Jeremiah anticipated an age without its presence (3:16). It was presumably lost during the destruction of Jerusalem by the Babylonians in 587 bc. There was no ark in the second Temple (Josephus, BJ 5. 219).

Gold-overlaid wooden receptacles or portable shrines are known from the ancient Near East in pre-Mosaic times. The ark is unique, however, as the repository of the covenant-tablets, i.e. documents bearing the 'covenant-stipulations' (edut). [The New Bible Dictionary, (Wheaton, Illinois: Tyndale House Publishers, Inc.) 1962.]

From The Wycliffe Bible Dictionary:

ARK OF THE COVENANT. This was a chest made of acacia wood, about four feet long, two and a half feet wide, and two and a half feet high. It was overlaid with gold inside and out (Ex 25:11) and a ring of gold at each corner or foot through which poles were passed to carry it. The lid of the ark, the kapporeth or "mercy seat" (Ex 25:17), was made of pure gold. At each end of the mercy seat was a cherubim made of hammered gold.

The ark (áaron) is referred to some 200 times in the OT under 22 different designations. It is called the ark (Ex 25:14), the ark of Jehovah (I Sam 4:6, ASV), the ark of God (Elohim, (I Sam 4:18), the ark of the covenant (Josh 3:6), the ark of the testimony (Ex 25:22). This various terminology for the ark may reflect a difference in date and authorship of the various sources, but this is not necessarily so.

The ark seems to have served various functions during its history. It was built by Moses (Deut 10:5), or actually by Bezaleel (Ex 31:2, 6-7; 37:1-9), at Sinai. According to Num 10:33-36 it served as a guide to Israel in the wilderness, and Num 14:44 adds that when the rebels at Kadesh-barnea went out to possess the Promised land, neither Moses nor the ark went with them. In these passages the ark serves as a symbol of the presence of God. The ark is spoken of as the throne of God (I Sam 4:4; II Sam 6:2; cf. Jer 3:16).

The idea of the ark as a war palladium is a very common one in the OT. The ark was very prominent in the story of the capture of Jericho (Josh 6-7), and in the struggle with the Philistines when the ark was captured (I Sam 4:11), at which time it is said that "the glory is departed from Israel" (I Sam 4:21). Even in defeat God did not abandon His throne on the ark but wrought havoc among the Philistine captors. The power of the ark can be seen in the curses it brought upon the Philistines (I Sam 5) and upon Uzzah (II Sam 6:7). G. Henton Davies has urged that the ark may be mentioned a number of times in the Psalms under the term `oz, "strength" (cf. "The Ark in the Psalms, Promise and Fulfillment", F.F. Bruce, ed.; also cf. Ps 132:8; 78:59-61; 105:4).

One other function of the ark was to serve as the container of the tablets of the law or covenant. This concept is reflected in the name "the ark of the testimony" (Ex 25:16; Num 4:5; Josh 4:16).

When the ark was returned from the Philistines, it came to Beth-shemesh (q.v.) and then was removed to the house of Abinadab in Kirjath-jearim where it stayed for approximately 20 years, (I Sam 7:2). Although the ark was now in Israel, it was probably, in effect, still under the control of the Philistines. This fact would explain why Saul had nothing to do with the ark and why "all the house of Israel lamented after the Lord" (I Sam 7:2). [Pfeiffer, Charles F., Wycliffe Bible Encyclopedia, (Chicago, IL: Moody Press) 1975.]

From Unger's Bible Dictionary:

ARK OF THE COVENANT (Heb. aroôn, the common name for a "chest" or "coffer").

Names. It was called the "ark of the covenant" (Numbers 10:33; Deuteronomy 31:26; Hebrews 9:4; etc.), because in it were deposited the two tablets of stone upon which were written the Ten Commandments, the terms of God's covenant with Israel; "the ark of the testimony" (Exodus 25:16, 22), the commandments being God's testimony respecting His own holiness, and the people's sin; "the ark of God" (1 Samuel 3:3; 4:11), as the throne of the divine presence. For full description, see Tabernacle.

History. The history of the Ark is in accordance with its intensely moral character. As the symbol of the Lord's presence, it was borne by the priests in advance of the host (Numbers 10:33; Deuteronomy 1:33; see also Psalm 132:8). At its presence the waters of the Jordan separated; only when it was carried to the farther shore did the waters resume their usual course (Joshua 3:11-17; 4:7, 11, 18). The Ark was carried about Jericho at the time of its downfall (Joshua 6:4-12). Very naturally, the neighboring nations, ignorant of spiritual worship, looked upon the Ark as the god of Israel (1 Samuel 4:6-7), a delusion that may have been strengthened by the figures of the cherubim upon it.

The Ark remained at Shiloh until the time of Eli, when it was carried along with the army, in the hope that it would secure victory for the Israelites against the Philistines. The latter were not only victorious but also captured the Ark (1 Samuel 4:3-11); but they were glad to return it after seven months (1 Samuel 5:7). It was taken to Kiriath-jearim (1 Samuel 7:2), where it remained until the time of David. Its removal to Jerusalem was delayed three months by the death of Uzzah while carelessly handling it. Meanwhile it rested in the house of Obed-edom, from which it was taken, with greatest rejoicing, to Mt. Zion (2 Samuel 6:1-19).

When the Temple was completed, the Ark was deposited in the sanctuary (1 Kings 8:6-9). In 2 Chronicles 35:3 the Levites were directed to restore it to the Holy Place. It may have been moved to make room for the "carved image" that Manasseh placed "in the house of God" (2 Chronicles 33:7), or possibly on account of the purification and repairs of the Temple by Josiah. When the Temple was destroyed by the Babylonians the Ark was probably removed or destroyed (2 Esdras 10:21-22). Sacred chests were in use among other peoples of antiquity, and served as receptacles for the idol, or the symbol of the idol, and for sacred relics.

BIBLIOGRAPHY: Noah's Ark: A Heidel, Gilgamesh Epic and Other Old Testament Parallels (1946); J. C. Whitcomb, Jr., and H. M. Morris, The Genesis Flood (1962); J. W. Montgomery, The Quest for Noah's Ark (1972); J. Dillow, The Waters Above (1981). Ark of Bulrushes: M. Jastrow, Jr., Jewish Encyclopedia (1946), 2: 578-79. Ark of the Covenant: J. Morgenstern, Hebrew Union College Annual 17 (1942-43): 153-266; id., The Ark, the Ephod, and the Tent of Meeting (1945); F. M. Cross, Biblical Archaeologist 10 (1947): 45-68; R. E. Hough, The Ministry of the Glory Cloud (1955); E. Nielsen, Supplements to Vetus Testamentum 7 (1960): 61-74; J. B. Payne, Theology of the Older Testament (1962); M. H. Woudstra, The Ark of the Covenant from Conquest to Kingship (1965).