The Catechism of the Catholic Church explains:
640 . . . The first element we encounter in the framework of the Easter events is the empty tomb. In itself it is not a direct proof of Resurrection; the absence of Christ’s body from the tomb could be explained otherwise.
Nonetheless the empty tomb was still an essential sign for all. Its discovery by the disciples was the first step toward recognizing the very fact of the Resurrection.
This was the case, first with the holy women, and then with Peter. The disciple “whom Jesus loved” affirmed that when he entered the empty tomb and discovered “the linen cloths lying there”, “he saw and believed”.
This suggests that he realized from the empty tomb’s condition that the absence of Jesus’ body could not have been of human doing and that Jesus had not simply returned to earthly life as had been the case with Lazarus.