Entity Properties are gettable, and sometimes settable aspects of anything which can move, such as an item, a mob, or a player. They can be used in Message Routines to see the value, or in conditionals to check the value. They have a value, and a value type, such as Integer, String, Block, or even another Entity. The format here will show the (Type) then how to use it - And a brief description of it.

• (Enum) {item}_type - For example player_wielded_type Returns a Bukkit Enum unless aliased by TypeNames.
• (Enum) {entity}_type - For example attacker_type, among many possible results.
• (String) {player}_name - The name of the player referenced, if applicable.
• (Entity) {entity}_vehicle - For any entity that has a passenger, for example minecarts or spiderJockeys.
• (World) {entity}_world - Gives the world name based on where the entity was.
• (List) {entity}_tags - A list of all integer tags on the entity.
• {player}_displayname - The nickname that is used in chat.
• {player}_playerlistname - The string that is displayed on the Tab menu
• {block}_line({integer}) - The exact string on that sign, at line number {number}.

• (String) {entity_customname} -
• (Boolean) {entity_customnamevisible} -
• (Entity) {entity}_owner - Only applicable to Ocelots and Tamed_wolves.
• (Entity) {entity}_target - The entity being chased/attacked by the {entity}.
• {entity}_passenger - Returns any entity riding on another, such as a boat passenger.

Relevant

All Integer Variables are also usable in the same way, but will (as expected) show a number, not a word.