Raw parse tree

In plain English

The first thing PostgreSQL builds from your SQL text is a raw parse tree: a structural representation of the sentence produced purely from grammar. It captures what you typed without checking whether any of the tables or columns actually exist.

Why it matters

This is the only stage where a syntax error can occur. Because it does no catalog lookups, a query can parse perfectly and still fail a moment later at the analysis stage with “relation does not exist”. Knowing the split tells you which kind of error you are looking at.