There are 2 types of work permits: open work permits and employer-specific work permits.

Open work permits

An open work permit allows you to work for any employer in Canada, except for an employer:

who is listed as ineligible on the list of employers who have failed to comply with the conditions or
who regularly offers striptease, erotic dance, escort services or erotic massages
You can only get an open work permit in specific situations. Find out if you can apply for an open work permit.

Employer-specific work permits

An employer-specific work permit allows you to work according to the conditions on your work permit, which include:

the name of the employer you can work for
how long you can work
the location where you can work (if applicable)

There are many options for obtaining a Canadian work permit. Some work permits require a job offer from a Canadian employer, while some others require that the employer provide a Labour Market Impact Assessment (LMIA).