Coming from Oracle SQL

I have a dumb question to ask - as I'm certain all of my future ones will
be as well. I am coming from the Oracle SQL PL/SQL side of things and
trying to get wrapped around PostgreSQL. I used to find tables in Oracle
by using the following query and hoped to find a replacement. Better
would be someplace to reference these sorts of "key" tables, etc that keep
track of the indexes, tables, columns and more.

select distinct table_name from all_tables;

Thank you for the help - you will never know how appreciated it is!
Ronni