Lots of symbols have their pronunciations. For instance, "$\tbinom {n}{k}$" is pronounced "$n$ choose $k$", and "$\forall$" is pronounced "for all".
The symbol "$\mapsto$" is used to represent a mapping, as in
$$x \mapsto f(x)$$
How to pronounce this symbol?
There's no fixed pronunciation - I've heard each of "maps to," "goes to," "is sent to," and further variations.
Keep in mind that there are lots of mathematical symbols with no fixed pronunciation: for example, "$\forall$" is pronounced as each of "For all," "For every," "For any," or "For each" with reasonable frequency (although personally I think the first two are the best choices and I strongly object to "For any").