Minecraft wiki entry for Resource_location, associated text: Hardcoded contents
Cat types for predicates (e.g. textures/entity/cat/tabby.png, textures/entity/cat/jellie.png)
Criteria triggers
Item properties (i.e. item predicates in models. e.g. angle, custom_model_data)
Loot context param sets (i.e. types of loot table. e.g. barter, generic)
Unaccessible contents:
Suggestion providers for autocompletion of commands (e.g. summonable_entities, all_recipes)
Entity models
Loot context params (e.g. this_entity, origin, tool)