Ancient Israel was commanded to build temples as Houses in which the Lord their God would dwell. The Temple or בֵּית הַמִקְדָּשׁ, was God's Sanctuary, the House Of Holiness, and his people served him according to the several ways He directed they should do.
Local Jewish congregations met in Synagogues that were markedly dissimilar to the Temples of their fathers. When Christianity left its Jewish roots it adopted the forms of service of the Synagogue in its Churches and thenceforward considered Temples and Temple worship redundant.
As part of the 'restoration of all things,' Latter-day Saints were commanded to build temples. Today's Temples are different in from ancient Temples although they have much in common. Both ancient and modern Temples are designated as God's Houses, and serve holy purposes as directed by Almighty God.
Yet, as some keen-eyed critics have noted modern temples have little in common with ancient temples with regard to their form and ritual function. That is no surprise to Latter-day Saints who do not expect post-meridian temples to serve the same functions as ante-meridian temples any more than the Mosaic Code is expected to serve the same purpose as the Gospel of Jesus Christ. That there is a connection is undisputed but it would be a facile argument that Christianity is not right because it does not resemble Old Testament ritual practices. It is equally facile to complain that modern temples do not function in the same way as did Israel's ancient sanctuaries.
The Mosaic Temples served the requirements of the Mosaic or Levitical Law, but when Jesus came and was crucified the Mosaic Temple's veil was 'rent in twain.' It was the end of ancient temples. In this Dispensation of the Fulness of Times, the Lord God commanded Latter-day Saints to build temples that would serve his purposes of endowing the Saints with power from on high and also of performing essential saving ordinances by proxy for our kinfolk that have not heard the Gospel of Jesus Christ with the purpose of affording them the opportunity to accept Jesus Christ after they were dead, and to be judged worthy to be saved in the Kingdom of Heaven. The proxy ordinances are proof of our love for our forbears and acts of Mercy by God the Father of us all.
The prophet Obadiah told of a day to come in which saviours would stand on Mount Zion.
“And saviours shall come up on mount Zion to judge the mount of Esau;
and the kingdom shall be the LORD'S.” --Obadiah 1:21
Latter-day Saints believe those that search out their ancestors and are baptised in their behalf as proxies are the saviours spoken of by Obadiah. That is why we build temples, for our own blessings and so that our ancestors that have not known Jesus Christ may also share the same blessings and be exalted.
Further Information about Latter-day Temple Work at:
Salvation For the Dead
Exaltation to godship - Deification
More about Salvation For The Dead