"Architect" and "designer" get used interchangeably in casual conversation, but they're not the same thing, and the difference matters a lot more once your project actually needs a permit. Here's what licensure means in practice and why it affects who you should hire for what.
A licensed architect has completed an accredited professional degree, several years of supervised experience under the Architectural Experience Program, and passed the Architect Registration Examination — a rigorous, multi-part test covering structural systems, life safety, building codes, and construction administration. That license is what allows an architect to legally stamp construction documents, which most jurisdictions require before they'll issue a building permit for anything beyond minor cosmetic work.
A designer — sometimes called an interior designer, a design-build consultant, or simply a "home designer" — may have real talent and experience creating beautiful concepts and space plans, but generally cannot stamp construction documents or take legal responsibility for a building's structural and life-safety compliance. For smaller cosmetic projects, that limitation may not matter. For anything involving structural changes, additions, new construction, or a commercial permit, it matters a great deal.
This isn't a knock on designers — many are excellent at what they do, and plenty of successful projects involve both a designer for interior finishes and an architect for the structural and permitting work. The mistake to avoid is assuming a beautiful concept rendering means the project is ready to build. If your project needs a permit (and most additions, new construction, and commercial work do), you need a licensed architect's stamp on the construction documents at some point in the process, whether or not a designer is also involved.
When you're evaluating who to hire, ask directly: are you a licensed architect, and can you stamp construction documents for this project's jurisdiction? A straightforward answer to that one question will tell you most of what you need to know about whether you're talking to the right person for your project's scope.