Is saying welcome a greeting?

Excuse me, could you please clarify something for me? I came across this paragraph that asks, "Is saying welcome a greeting?" and I'm a bit confused. I've always thought of "welcome" as a polite phrase used to acknowledge someone's arrival or presence, but I'm not entirely sure if it qualifies as a greeting in the traditional sense. Could you please elaborate on whether "welcome" is indeed a greeting, and if so, how it differs from other more conventional greetings like "hello" or "hi"? Thank you for your time and expertise on this matter.