The most common type of work permit is an employer-specific work permit under the temporary foreign worker program which entails a job offer and an LMIA.  

An employer-specific work permit lets you work in Canada according to the conditions on your work permit, such as: 

• the name of the specific employer you can work for 
• how long you can work 

• the location where you can work (if applicable) 

Most of the time for obtaining a work permit: 

• You need to get a job offer from a Canadian employer before you apply. 
• The employer must apply for a Labour Market Impact Assessment (LMIA) from Employment and Social Development Canada (ESDC). 
• ESDC will decide whether the employer can hire a foreign worker to fill the job. 

Generally, to obtain a work permit, a Labour Market Impact Assessment (LMIA) must first be conducted and approved. As part of the LMIA process, Canadian employers must demonstrate that employing a foreign worker will have a positive or neutral impact on the Canadian labour market, and that there is currently no Canadian citizen or permanent resident available to fill the position, which is typically done by advertising the position on several venues. Because of the reluctance to hire a foreigner for a position that could presumably be performed by a Canadian citizen or permanent resident, these applications are heavily scrutinized and are often refused if they do not conform precisely with requirements set forth by the government. 

Note that a foreign national cannot apply for an LMIA. Rather, LMIAs are documents which must be applied for by a Canadian employer.