What happens to transactions durring a pg_dump?

I'm trying to understand better what happens to a transaction that is commited in the middle of a pg_dump.  Is the transaction included in the database dump, or is it excluded.

Example

pg_dump starts
    - transaction is begun
      - row from table a is deleted
      - row from table b is updated
    - transaction is commited
pg_dump finishes

What happens to the deleted row and the updated row with respect to the backup file.

1.  If they are done before table a and table b are backed up?

2.  If table a is dumped and table b is not?

Thanks,

Chris