# Reference

Information-oriented technical description. Consult these pages when you need to
look something up, not to learn concepts (see {doc}`../explanation/index` for the
"why").

- {doc}`api` — the public classes: `Rule`, `Node`, `LiteralNode`, `NodeVisitor`,
  and the exceptions.
- {doc}`core-rules` — the RFC 5234 core rules available in every grammar.
- {doc}`bundled-grammars` — the 30+ RFC grammar modules in `abnf.grammars`.
- {doc}`configuration` — class attributes and environment variables that change
  parser behavior.