Vanilla refers to The Binding of Isaac: Rebirth and its DLCs, without additional mods.
Isaac typically refers to the player, regardless of which character they are playing. If this is untrue, it will be clarified further in the description of the object.
Object(s) refers to the subject of a given page; for example, if you are looking at the Sprite Changes made by the Texture Pack, the object of the page would be sprites.
Sprite(s) refers to the art of an object and the way it appears in-game.
Collectible(s) refers to in-game items, such as Brimstone, Mom's Knife, and the like.
Luck-based Chance means that the possibility of the object's effect taking place increases in proportion to your Luck stat -- the higher your Luck, the more likely it is to happen.
Pick-up(s) refers to room drops and buy-ables alike to cards, chests, sacks, etc.
Core pick-up(s) refers to specifically Bombs, Coins, Hearts, and Keys.
Interactable(s) refers to objects that perform a particular action when Isaac collides with them, such as Slot Machines, Beggars, Confessionals, and the like.
Pocket item(s) refers to specifically Cards, Pills, Runes, and similar one-time use pick-ups.
Soul Heart(s) refers to the pick-up of the same name, but can be interchanged with Black Hearts as necessary.
Suit-type refers to the suit (color and icon) of a playing card, and its associated pick-up type. This includes Clubs (bombs), Diamonds (coins), Hearts (hearts), and Spades (keys).
Room Rewards are pick-ups that spawn in the center of a given room after Isaac clears it of enemies. This does not refer to item pedestals or pick-ups obtained through other methods.
Special Room refers to any room on the floor that is not default, such as Libraries, Sacrifice Rooms, or Shops. This excludes Boss and Mini-Boss rooms.