Minecraft wiki entry for location, associated text:  biome: The biome the entity is currently in. Accepts these 73 values (see also Biome#Biome IDs).
 block: The block at the location.
 blocks: A list of block IDs.
 tag: The block Tag.
 nbt: The block NBT.
 state: A map of block property names to values. Test will fail if the block doesn't match.
 key: Block property key and value pair.
 key:
 max: A maximum value.
 min: A minimum value.
 dimension: The dimension the entity is currently in.
 feature: Name of a structure. Accepts these 15 values (see also Commands/locate).
 fluid: The fluid at the location.
 fluid: The fluid ID.
 tag: The fluid Tag.
 state: A map of fluid property names to values. Test will fail if the fluid doesn't match.
 key: Fluid property key and value pair.
 key:
 max: A maximum value.
 min: A minimum value.
 light: The light at the location.
 light: The light Level of visible light. Calculated using: (max(sky-darkening,block)).
 light:
 max: A maximum value.
 min: A minimum value.
 position:
 x: The x position.
 x:
 max: A maximum value.
 min: A minimum value.
 y: The y position.
 y:
 max: A maximum value.
 min: A minimum value.
 z: The z position.
 z:
 max: A maximum value.
 min: A minimum value.
 smokey: True if the block is closely above a campfire or soul campfire.