Making catalog current means switching between DBs. Remember initially I connected to (finance) DB, which made the (finance) catalog current. Then I "opened a second connection" to (finance_2021), which made that current catalog and so that select would give me all tables from (finance_2021).
I hope now its clearer.
No, it is not clearer. I suggest you show some code. Given what you've said my guess is you are not correct.
