Eyebrows can send body language. Being near the eyes, which are the major senders of signals, they are highly visible communicators, although the limited control of muscles around them can limit what they say.
When a person is surprised, their eyebrows are often raised. This typically happens as a part of opening the eyes wider, perhaps to see more clearly what is going on. The more the surprise. the higher the eyebrows are raised.
Raising the eyebrows asks for attention from others and can signal general emphasis. When as question is asked and the eyebrows are raised afterwards, this is a clear invitation to answer the question.
Opposite to the dominant lowering of eyebrows, raising eyebrows is may be a submissive move or indicate openness, as it lets the other person see your eyes ('I am not looking where I should not!').
Raising a single eyebrow is something that only some people can do and can be a bit more wry in its meaning, for example asking 'Are you sure?' when the other person appears to be talking with limited accuracy.