There are two types of Canadian work permits, they are LMIA based work permits (which are employer specific) and open work permits (which are not employer specific). If you wish to obtain an employer specific work permit then an employer will need to obtain a positive LMIA which is approved by Service Canada which is needed when applying for a work permit to IRCC. For open work permits, there are various different types and situations where an open work permit may be an option for a foreign national. They range from spousal open work permits to, bridging open work permits to post grad work permits to name a few.
The International Mobility Program (IMP) lets an employer hire a temporary foreign worker without the need for a Labour Market Impact Assessment (LMIA). There are over 40 exemption codes that fall under the IMP.
Job offers are typically submitted through an employer portal and must meet certain criteria to be considered a valid job offer.
A very common type of open work permit for students who have completed their program of study is the Post Grad Work Permit or (PGWP). This, if a student meets the eligibility criteria, can allow a student to work for between 1 and 3 years for any employer and potentially help one meet the work experience needed for a particular Permanent Residency stream such as a PNP program or CEC.