Written Torah provides two verses that directly answer what is the Tabernacle:
YLT Exodus 25:8 'And they have made for Me a sanctuary, and I have tabernacled in their midst;
YLT Lv 26:11 'And I have given My tabernacle in your midst, and My soul doth not loathe you;
After giving the 10 commandments and the Written Torah at Mt. Sinai, Yahuah asked Moses to create a sanctuary for Him, so that He could dwell (tabernacle) among His people. This was the Tabernacle, in Hebrew known as Mishkan.
The Mishkan (Tabernacle) was a portable sanctuary, a spiritual center in the middle of the desert. It was the place where the Children of Israel would bring slaughters to atone for sins or express gratitude. It was the place where Yahuah God would communicate with Moses and Aaron, His voice emanating from between the two cherubim on top of the Ark of the Covenant in the Holy of Holies section of the Tabernacle Mishkan. It was the place where Yahuah was close to His people. The presence of the Tabernacle Mishkan was a sign of approval from God and His satisfaction with the Children of Israel.
How did it happen:
After the Golden Calf incident and following plague and forgiveness, the command finally came. The Tabernacle would be a sign of the renewed closeness between Yahuah and the Hebrews.
Yahuah specified that the work be overseen by Bezalel from the tribe of Judah, who was joined by Oholiab from the tribe of Dan. The people were commanded to make a voluntary offering (terumah) and donate materials and labour to work on the building, such as weaving and crafting. Within a short time, probably around one year, the entire structure was complete.
What was Tabernacle Mishkan?
The Mishkan sat inside a large Courtyard that was 120 cubits long and 60 cubits wide (a cubit is approximately 18 inches, or 46 cm). The courtyard was surrounded by a linen partition which was 100 cubits in total length and 50 cubits in total width, held up by wooden pillars and copper sockets and fastened to the ground with stakes. In the center of the eastern half of the courtyard stood the large copper altar, which was used for animal slaughters. The altar was square, 5x5x3 cubits, which was the perfect size for sons of Aaron to access it and to fit the slaughtered animals. Between the copper altar and the entrance of the Tent of the sanctuary stood the Copper Laver where the priests would wash their hands and feet.
The sanctuary, the Tent of the Taberncle itself was 31 cubits long and 10 cubits wide. Its walls were made of thin, gold-plated, acacia-wood boards standing side-by-side to form three sides of a rectangle. The beams were inserted into interlocking silver sockets and were held in place by long, gold-plated, wooden poles. The Entrance curtain hangings covered the fourth side and served as the entrance into the Mishkan.
The first, the bottom covering of the Tabernacle was a tapestry, woven of linen and red, blue, and purple wool, with cherubim embroidered on it. The tapestry consisted of the two separate sections, which were connected together by a row of 50 golden clasps. The tapestry was covered by a second covering, a layer of goat hair, with its halves similarly attached with the 50 copper clasps. These two layers covered the top of the structure and hung over the wooden walls of the Mishkan. Additionally, red-dyed ram skin covering, which was probably one long piece and so-called "Tachash" (or "darkened) skin covering covered the roof of the structure.
What was inside the Mishkan Tabernacle?
The interior of the Tent of the Mishkan was divided in two by a hanging tapestry. The front room, known as the Kodesh (the Holy Place), contained special furniture. On the southern side stood the golden menorah (lamp), whose lamps on the seven branches the priests kindled every morning and every evening. Near the northern wall stood the golden table, upon which the priests placed 12 ritual show-breads every week for them to eat during their service in the Tent of the Mishkan. There was also a smaller golden altar upon which the special psychoactive incense was offered continuously during the Tabernacle service.
The second, western room was known as the Kodesh HaKadashim, the Holy of Holies or the Ark of the Covenant room. The Holy of Holies contained the Ark of the Covenant: a golden box that housed two stone Tablets written by God (this was the second copy, first being broken by Moses at the Calf incident). There was nothing in the Ark of the Covenant except for the two tablets of the covenant. Later, the Holy of Holies featured other sacred items, namely the jar of manna that Hebrews ate for 40 years in the desert and the Aarons rod that was budding with almonds. On the cover of the ark there was a golden slab (cover or shelter) with two golden cherubim facing each other with outstretched wings and covering the slab (cover) from view with them.
No one was permitted to enter the Holy of Holies except for the High Priest, and even he would enter only once a year as part of his Yom Kippur service. And only the sons of Aaron were allowed inside the Tent of the Tabernacle.
The Mishkan was made to to be portable on purpose. In fact, many of its contents were outfitted with special carrying poles and protective coverings. There were also six special covered wagons that were used to transport the Tabernacle parts, such as the boards, sockets, curtains e.t.c
Dedication and Anointment of the Tabernacle (Mishkan)
For a week, Moses was setting up the Mishkan. Then, on the first of day of the second year from the Exodus from Egypt, Moses officially inaugurated and anointed the Tabernacle. The entire tent was filled with Yahuah’s Presence in a form of pillar of fire or smoke, which prevented everyone – even Moses – from entering the Tent of the Mishkan.
For the next twelve days, the princes of the twelve Tribes of Israel brought slaughters and gifts. The Tabernacle was not the exclusive property of its keepers, the Levites and the Priests, but was the heritage of every Hebrew who helped to build it.
How long did the Tabernacle exist?
The Tabernacle traveled with the Hebrews for 40 years in the desert. When the people entered the Land of Canaan (Israel), the Mishkan came with them. For fourteen years, the Mishkan stood in Gilgal while the Hebrews conquered and allotted the land. Then they placed the Tabernacle in Shiloh. The sanctuary stood in Shiloh for 369 years. At the end of that period, the sanctuary was moved to Nov, and then to Givon. The last reference to the location of the Tabernacle and its parts is mentioned in the apocryphal book of Maccabees, where it is said to have been hidden by Jeremiah in the mount Nebo, where Moses died. Current location of the Tabernacle or its existence is unknown.
When Solomon built the 1st Temple in Jerusalem, he decomissioned the Tabernacle for some reason. However, Written Torah explicitly states that only Tabernacle and NOT Temple is the true, explicitly commanded dwelling of God Yahuah FOREVER and FOR ALL ETERNITY. Tabernacle Mishkan should always exist and if it does not it is our responsibility to rebuild it. So it is very unclear why current traditional Judaism has completely forgotten this.