Does the subject want to ask, "Are a hollow point and a solid point in the set obtained?" Solid ones are ok, but hollow ones are not. Solid means that the number of points is in the represented set; Hollow is not in the set, just outside the set. Set is a basic concept in mathematics and the research object of set theory. The basic theory of set theory was not founded until19th century. The simplest statement is the definition in the most primitive set theory-naive set theory, and the set is "a bunch of things". The "things" in a set are called elements. A whole consisting of one or more definite elements is called a set.