currval question

I am trying to get the last value updated by an column auto-incrementing
with nextval(). In MySQL, you'd use LAST_INSERT_ID() - in Postgre, currval()
appears to do the trick.

Is this maintained on a per-connection basis? For example, user A inserts
and the nextval() updates to 5, user B does 2 inserts, updating nextval() to
7. When user A calls currval() they should get 5 if the updates are per-cnx.
What does psql do under the hood here?

thx
a