This is the 47th most frequent German word.
was
"Was" means "what" in English.
In this sentence, 'was' serves as an interrogative pronoun to ask about an action or activity.
Was machst du gerade?
What are you doing right now?
In this example, 'was' again serves as a relative pronoun to denote something undefined that is being specified by the clause 'mir schmeckt'.
Ich esse das, was mir schmeckt.
I eat what I like.
Here, 'was' is used as a relative pronoun to indicate the subject of the verb 'expected'.