It is a type of work permit that enables you to enter into a foreign country and work there for a particular period of time. Without a work visa, you cannot work in a foreign country. Different countries may have different procedures and criteria for issuing work permit visas. Work permit visas are issued either on temporary or permanent basis. A temporary work visa remains valid for a particular period of time after which the visa holder needs to renew, if his employer wants to extend his (employee’s) stay.
Normally, it is the employer who applies for a work permit visa on your behalf. Work visas require an employer to contact the immigration authority of a particular country and get approval.