Minecraft wiki entry for JSON_format, associated text:  conditions:
 block: The block that was placed. Accepts block IDs.
 item: The item that was used to place the block before the item was consumed.
Tags common to all items[show]
 location: The location of the block that was placed.
Tags common to all locations[show]
 state: The block states of the block.
 <state_name>: A single block state, with the key name being the state name and the value being the required value of that state.
 player: The player that would get the advancement. May also be a list of predicates that must pass in order for the trigger to activate.
All possible conditions for entities[show]