Common is the name used for a widespread creole language that blends aspects of many regional and racial tongues. Few populations use Common as a primary language. Generally travelers throughout the world can reasonably expect to find at least some Common speakers, but it is usually adopted as a second or third tongue.
A language born of necessity, Common is a creole of many dialects of the world, encompassing vocabulary and structure in which speakers of diverse languages all might see a passing resemblance. However, it is very much a language in its own right with its own specific characteristics and quirks, and not generally mutually intelligible with any other language. Common is frequently adopted to make communication between culturally disconnected peoples easier - if needed vocabulary doesn’t already exist, it is simply adopted from whatever language can provide it.
As a consequence of how the language developed, hand (or other appendage) gestures are used with great frequency to help communicate ideas the speakers cannot quite get across through speech alone.