running postgres

may this be a silly doubts but , i am new to postgres, please answer to
these::

 /usr/local/pgsql/bin/psql test
test=#


 sudo su postgres -c psql template1
template=#


what is the difference between the above two and,
why is the path different in both cases
which should i use now


how can i create a user  in test or template
when i give create user
it is asking for create role , how should i create role?



Thanks & Regards
 kusuma.p