Identifiers are names for objects. You can find them everywhere, for entities, attributes, namespaces, relations and types...
They are composed of word characters, so any snake_case or CamelCase notation will be fine.
Here is their specific regex: \b[a-zA-Z_][a-zA-Z0-9_#]*\b
.
If you need to include other characters, such as spaces or special ones, you can escape them using "
.
Here are valid identifiers:
posts
post_authors
"user events"