It was customary in ancient Israel to place important or wealthy people in tombs and to close up the tombs with a large rock. Only wealthy families could usually afford this kind of burial place.
The gospel accounts differ as to how many men or angels appeared in this interaction. It is likely that the men were angels, but how many of them were there is unclear. It is best to translate this as it appears in the ULB without trying to reconcile these passages. (See: [Matthew 28:1-2](../../mat/28/01.md), [Luke 24:4](../../luk/24/04.md), and [John 20:1-2](../../jhn/20/01.md))