Possible relocation from US to Belgium

If you wanna live in Belgium for over 90 days, you gotta apply for a long-stay visa and residence permit. What docs you need depends on why you're stayin', like work, school, fam, or biz. Once ya get there, you gotta register with the local gov so they can give ya an ID number and a card for residency. Check out the official Belgium websites or hit up the closest consulate or embassy for more deets.

A work permit is a document that gives the right to work in Belgium. There are different types of work permit: some give you the right to do a specific job at a specific employer, other permits give you the right to participate freely on the Belgian job market (so you can change jobs without needing to change the permit). These documents have their own rules and conditions before being granted.

A residence permit is the permission to stay on Belgian territory. Believe it or not, but countries like to tightly control who resides (= lives) on their sovereign territory. That is what the residence permit and all it's rules is about. Usually a country allows a non-national to stay within its borders for a prolongued duration (so not just visiting) for a specific reason. The most common reasons why Belgium allows third country nationals to reside here are: because you are studying in Belgium, because you are working in Belgium or because you are reuniting with a select group of family members (such as spouses) that are already (legally) residing in Belgium.

Each of these types of residence permits has their own conditions and procedures.

The "combined permit" I is a single document (and unified application process) in which both the conditions for a work permit and a residence permit based on a work permit are applied for, examined and decided on.