In postgresql, what's the difference a “database” and a “relation”? ('error relation x does not exist', 'error database x already exists')

Question

I see the juxtaposition of these two errors and, given the dearth of Google search results, had to ask. What is the difference and what do I need to be doing here?

Answer 1

a relation is a table (or something that looks like one, eg a view), that is, it is a collection of rows, all with the same fields, and given some name to reference them by.

A database is a collection of relations and other entities (like triggers, functions and rules) that are kept together in some logical grouping.