There are many different kind of work permit applications inside Canada:
Graduate work Permit:-
After successful completion of college education from designated college or institute applicant is eligible to get minimum of one year of work permit or maximum of 3 years.
Closed work permit:-
One can get closed work permit as a result of Positive LMIA (formerly known as LMO labour market opinion).
Bridging Work Permit or LMIA exempt work permit:-
If applicant already got approved by Province Nomination or already applied for Permanent residence file than one can extent their work permit.