querying for specs?

I'm new to sql and to postgres.  I've spent quite a bit of time trying to
determine answers to the following questions, but have been unsuccessful.

Say you work at a small company, and the person who was db admin dies
suddenly.  How do you:

1) determine what db's postgres knows about?
2) how do you determine what tables exist, if any, in a given db?
3) how do you determine the structure/specification (not the data) of a table?

Thank you for any help you can offer.

--
                            - Martin J. Brown, Jr. -
                            - mjbjr@beaudesign.com -

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