Simplicity is the state or quality of being simple. Something which is easy to understand or explain is simple, in contrast to something complicated. Alternatively, as Herbert A. Simon suggested, something is simple or complex depending on the way we choose to describe it.
In some uses, simplicity can be used to imply beauty, purity, or clarity. Simplicity may also be used in a negative connotation to denote a deficit or insufficiency of nuance or complexity of a thing, relative to what is supposed to be required.