A work permit is the official approval that lets an expatriate take up paid employment with a named employer in a GCC country. It is distinct from the residence permit but is normally issued in tandem with it: the work permit authorises the job, while the residence permit authorises living in the country.
The issuing body differs by country, for example MOHRE in the UAE and the Ministry of Human Resources via Qiwa in Saudi Arabia. The permit is tied to a specific employer and often a specific profession, and changing jobs usually means transferring or reissuing it, sometimes requiring a no-objection certificate (NOC) depending on the country and reforms in force.
Work permits carry government fees, have a fixed validity, and must be renewed alongside the residence permit. Working outside the terms of the permit, or for someone other than the registered employer, can lead to penalties for both the worker and the company, so keeping the permit aligned with the real job matters.