I'm not sure what to call it it is a size medium from Forever 21

A girlfriend of mine gave this to me brand new it was too small for her it does fit small it is a medium and it was snog on me and I'm normally a small to a medium it's like new no signs of wear or tear it's really cute with anything that is like a tank top or something dressy underneath that's strapless or doesn't have to be shrimples but yeah I just it's hard to figure out at first at least for me it was but you put it behind you and then put your arms through it and it's it's really cute it adds something to the outfit but if you need better pictures of me now this one was kind of tough