Wiktionary
n. A simple device for binding a few to many sheets of paper, leaving the sheets intact; a strip of stainless sheet steel bent into the shape of an isosceles triangle with loops at the apex.
Wikipedia
A binder clip, or a banker's clip or foldover clip, is a simple device for binding sheets of paper together. It leaves the paper intact and can be removed quickly and easily, unlike the staple. The term "foldback clip" is used in the United Kingdom to describe this invention (not to be confused with a Bulldog clip, an older device with the same function, which is stronger and has rigid rather than folding handles). It is also sometimes referred to as a "handbag clip" because, when not in use, its clip can be up to look like a handbag.