Confussion with table-lock levels and isolation levels

Hi fellows !

I would only want to ask some questions concerning table-locking levels
and isolation levels:

* First of all:  should I assume that AccessXXXXXXX  modes imply locking
the complete table and RowXXXX imply locking only the  rows which have
been accessed ? Will then the conflicts be solved according the
hierarchy between modes ?

* Second:
          - What does exactly mean that a mode 'CONFLICTS'  with another
?
          - Does it mean that another concurrent transactions having
these modes will have to wait until the first transaction
          have finished (commit or roll back) ?
          - Can we determine (when accessing a row in a table) wether we
will have a conflict or not according to the criteria
          explained in the previous question (Access-> complete table,
Row -> rows accessed) ?

*Third:
     If all the previous assumptions are true:
               - When there is a conflict, will the only consequence be
that all concurrent transactions will be processed in a
               FIFO serie and not in parallel ?
               - What about all the others concurrent transactions which
haven't conflicted ? How can you avoid falling into
               contradiction with the isolation level (and assure the
protection against non-repeteable reads or phantom
               reads ?
               - I feel those two levels (transactions and isolation
levels) are two layers so the transactions will be
               processed according to a FIFO serie when exist any
problem concerning the isolation level or the
               table-locking. Is this a good way to describe the way
PostgreSQL manages the things ?

Thank you very much for your help.  By the way, is the first time i'm
subscribed to a mailing list so if I do anything inappropiate or strange
please tell me.

Best regards

Gabi     :-)