Also called: Query node, analyzed parse tree
In plain English
After parsing the syntax, PostgreSQL runs parse analysis and produces a query tree: the same statement, but with every name resolved to a real catalog object, every type checked, and shortcuts like SELECT * expanded. It is the meaning of your query, not just its shape.
Why it matters
This is the stage that raises errors like “column does not exist” or type mismatches. The query tree is also what the rewriter and planner consume, and the normalized form you see in tools like pg_stat_statements reflects it.