What does John 20:8 mean?

Mary Magdalene rushed to tell the disciples that she'd found Jesus' tomb open and vacant. Peter and John arrive, but only Peter enters. There, they see the linen in which Jesus was buried lying empty. Peter, from his position inside, also notices that the face cloth (John 11:44) is separate from the other strips and has been neatly folded (John 20:1–7).

Legends about this folded cloth suggest it was a signal, used at a dinner, implying that Jesus planned to come back. This is not supported by any historical or scholarly evidence. The mere fact that the cloth is there, deliberately placed, and by itself, is evidence enough that it was put there on purpose. John comes into the tomb to see this, probably because Peter tells him what he has seen.

Looking at this piece of evidence gives John a jolt of realization. Despite Jesus' many predictions (John 2:19–22; Mark 9:31; Luke 18:33), the disciples are still having a difficult time understanding the idea of His death and resurrection (John 20:9). With two thousand years of hindsight, we might find that strange. In the moment, however, it's not clear what has happened. Seeing the folded cloth immediately tells John that it was Jesus—alive—who put it there.