List of tables with a query

Hi everybody,

I'm a novice in postgres database administration.
I'm looking for the tables or views witch containt the list of my
database 's objects. I know that a psql command "\d <table_name>" give
me the detail of my <table_name>, but i want to have the same result (or
something similar) with a query. Is it possible, for example, with
postgresql 6.5, to have the list of my tables (or all the columns of all 
tables ) with a single query ? 

Thanks for all your answers (and sorry for my bad english)