The word for temple, ναὸν [naon] has two general meanings in relation to the house of God in Jerusalem. (1) In a narrower sense, the inner sanctuary within a sacred precinct (τὸ ἱερόν [to hieron] ) where the divine being resides shrine, (inner) temple (Mtt. Mat. 27:1.51); (2) in a broader yet specific sense, the sanctuary in Jerusalem consisting of the (outer) Holy Place and the (inner) Holy of Holies temple (Mtt. Mat. 26:1.61).1
for the Lord God Almighty and the Lamb are its temple
For most of history, God had purposed that there be a Temple to mitigate His holy presence in the midst of sinful men. Now there is no more sin and man and God can enjoy full fellowship without separation (John John 1:1). It was the redemptive work of Jesus on the cross which ultimately restored full fellowship between man and God (Mtt. Mat. 27:39; John John 2:19; Col. Col. 1:19; Rev. Rev. 5:9+). See Temple of God. Significantly, God the Father and God the Son are equally considered to be the Temple. Again, we see the equivalency of Jesus Christ with the Father. Jesus is God (John John 10:30; Col. Col. 2:9; Rev. Rev. 1:8+, Rev. 1:18+)! See commentary on Revelation 1:8 and Revelation 1:18. Almighty is παντοκράτωρ [pantokratōr] . See commentary on Revelation 1:8. Concerning Jesus title as Lamb, see commentary on Revelation 5:6.