A salutation is a greeting, whether it's "Dear sir" in a letter or "Hey there!" in person.
The expression "Greetings and salutations!" contains two words meaning pretty much the same thing: A salutation is a form of greeting. In a letter, the salutation is the part that says "To whom it may concern" or "Dear John." When we talk, we give salutations like "hello," "hi there," "hey," and "welcome." Another more formal type of salutation gives honor to others — like a salute.
