some questions about POstgreSQL

Good (select CURRENT_TIME;), Postgres users!

    I'm going to migrate from MySQL to Postgres, but I can't understand
some things in Postgres :( Please help me :)

1. MySQL has a tool called "mysqlshow". It shows the structure of specified
table (column names, types, constraints, default values etc.). How to get such
data in Postgres?

2. How to make a group of users? For now  I see only one way -- to insert
something in pg_group class directly. But I want to know a structure of this
class ;)

3. Security question. I've created a database for some user, he is  DBA for it,
he can do anything with this database ("user"). After this I'm creating another
user ("hostile").  And he's also getting full access to this database :( He can
create own tables etc. Both users, by the way, do not have system UIDs, they use
password authentication. I see only one way to restrict the access to specified
database : describe it in special string in pg_hba.conf, use password auth with
special file which will contain a restricted list of users who really should
access this database. The rest of restrictions may be defined by grant/revoke
commands.

4. Is there some documents describing Postgres's system tables (pg_*) ? It seems
that it's  possible to get a lot of use from such information...

5. Does Embedded SQL allows to use password auth when connecting to database? It
seems it does not allow :(

I will be very grateful for any advice!

--
   Nickolay G. Grygoryev                shadow@aanet.ru
   St.Petersburg, Russia                2:5030/580@fidonet