What’s the Difference Between a Re-buy and a Re-entry?

A tournament re-buy can usually be made immediately when a player loses all
their chips. But it is generally during a specified time/level. Re-entry in a
tournament requires a player who has lost all their chips to physically re-register.
They often receive a new seat/table assignment. I call either one Zombie
tournaments…the player is not really dead after being felted.