query concerning vacuum and tablespaces

Hi

I have two general questions:

Let's say I vacuum a table called 'foo'. Does that release memory for
subsequent reuse by table 'barr'? Or is the marked memory restricted
solely for later reuse by table 'foo'? I get the impression the latter
is the case. I'm I mistaken?

Is it possible to move an already populated table or index from one
tablespace to another?

Thanks so much!