What you probably mean is
is a term; it's a "name"; it names a particular set; it doesn't make an assertion.
is not a term, but rather it's a formula; it makes an assertion (once we agree on what 'B' stands for, or, alternatively, once we decide it should be taken in the sense of a universal generalization on 'B').
You very much need to get that logic book I recommended, as soon as possible; it will get you on the right track to writing correct symbolizations.
The earlier formula you gave was
That is equivalent to:
For all B (If B is a subset of B, then A is subset of B).
An A that satisfies that is B itself, or any other A that is a subset of B, depending on what B is.
Though maybe you've not rendered the formula correctly (it is rather odd)?