There were two curtains at the Jewish temple. One curtain separated the temple court from the courtyard and would be the most visible. This outer curtain had heavenly imagery embroidered on it. The other curtain separated the innermost Holy of Holies from the rest of the temple. This inner curtain is described in Exodus 26:31–33, Exodus 26:35.
Most commentators understand that the inner curtain is the one that was torn in two. This would then show that access to God was no longer provided by temple sacrifices but by the unique sacrifice of Jesus. The fact that it was torn in two from top to bottom shows that God is the one who has done it.
38 And the curtain of the temple was torn in two, from top to bottom.