I have an exam tomorrow and I can't tell the difference between the 3 definitions

.

Say V is a space over F.

Subspace S is:

1) a subset of V

2) a space itself over F

Span(S) is:

1) a linear combination of elements in S

2) a space itself over F

Someone told me the other day that if S is a subspace, then S=span(s). Why? I can't tell the difference between span(S) and S.

If span(s) a subspace, what is it's superset - S or V? Neither?

And what is a spanning set and how it connects to span(S)?

I'd much appreciate a concrete example, thanks