In practice, both terms describe firms that design and build websites. But the distinction in how they operate is real and matters when you're choosing a partner for a B2B website project.
A web design company typically functions as a production shop. They're efficient at executing against a brief you provide: here's our messaging, here's our brand guidelines, here's what we want the site to do. They build it. This works well when your positioning is clear, your messaging is locked, and you need quality execution without upstream strategic work. Everything Flow operates this way — a Webflow execution shop for teams that have the strategy sorted.
A web design agency (in the fuller sense) typically brings strategic capability into the engagement. That means discovery and positioning work before wireframes, messaging architecture that drives information hierarchy, and design decisions grounded in buyer research rather than aesthetic preference. Everything Design works this way — the website is produced as the output of a brand strategy engagement, not as a standalone creative project.
For B2B companies, the difference matters because B2B websites fail more often at messaging than at aesthetics. A site that looks polished but doesn't communicate the right thing to the right buyer persona at the right moment in the sales cycle doesn't convert. If your brief is "we need a better looking site," a web design company is sufficient. If your brief is "we need a site that actually moves buyers through a decision," you need a web design agency with upstream strategic capability.