The difference between a visa and a work permit is important because each one governs something different.
Visa
A visa first of all allows you to enter a country and stay there. So it mainly governs your entry and the length of your stay. Depending on the country, there are different visas, for example tourist visas, student visas, or business visas. However, a visa doesn’t automatically mean you’re allowed to work in that country.
Work permit
A work permit, on the other hand, governs the right to work in a country. It’s an authorization from the authorities that you may work there legally. In many countries, the work permit is either applied for separately or tied to a specific visa, such as a work visa.