Re-entries in a tournament is when players are allowed to buy back in (re-entry) if they are eliminated while late registration is still open.
Re-buys in a tournament is when players are allowed to pay an additional fee and begin again or to purchase additional chips after falling below a certain amount of chips.
Add Ons is an option to purchase additional specified amount of chips at a specific time partway through a tournament. Unlike a re-buy, this option is granted to all remaining players regardless of stack size.
Freezeout is a tournament format in which the loss of all of one's chips permanently eliminates a player from the tournament. Freezeout tournament format does not offer players the opportunity to re-enter once eliminated. At the start of the tournament, the players will receive an equal amount of tournament chips. It is not possible to add-on more chips while the tournament is in play. If the tournament is not a re-entry or a re-buy tournament, then it will be a Freezeout tournament.