dictionary?

How do you accomplish this in pg?

1. Is there a table like the Oracle dictionary?
2. Is there a way to describe a table?

I use these all the time in oracle. When I can't remember where
some management metric is located in the system, I sort of grep for
it based on a keyword. For example, if I need to find out about some
snapshot (copy of a table from another db), I do this:

select table_name from dictionary where table_name like '%SNAPSHOT%';

TABLE_NAME
------------------------------
ALL_REGISTERED_SNAPSHOTS
ALL_SNAPSHOTS
...

SQL> describe ALL_SNAPSHOTS
Name Null? Type
----------------------------------------- -------- ----------------------------
OWNER NOT NULL VARCHAR2(30)
NAME NOT NULL VARCHAR2(30)
TABLE_NAME NOT NULL VARCHAR2(30)
...

select name from ALL_SNAPSHOTS;
...

TIA.