Does welcome mean hello?

I'm curious, could you clarify something for me? When someone says "welcome," does it always mean "hello"? Or could it have a different connotation depending on the context? For instance, if I'm at a store and the cashier says "welcome," is she just greeting me, or is she acknowledging my presence and readiness to serve? I'm interested in understanding the nuances of this phrase and how it might vary in different situations.