Based on: https://github.com/antlr/grammars-v4/tree/master/sql/postgresql

These folder contain base classes, grammar files and auto-generated parser.

* PostgreSQLLexer.g4: lexer definition - copied from antlr/grammars-v4 repo
* PostgreSQLParser.g4: grammar definition - copied from antlr/grammars-v4 repo
* PostgreSQLLexer.interp, PostgreSQLLexer.js, PostgreSQLLexer.tokens, PostgreSQLParser.interp, PostgreSQLParser.js, PostgreSQLParser.tokens, PostgreSQLParserVisitor.js: Auto generated by the grammar
* PostgreSQLLexerBase.js, PostgreSQLParserBase.js: Contain simple base classes and helper funtions required by the grammar.

You don't need to touch these files unless you're planning on updating the grammar. In that case, read the setup guide to know more.