A point set is a collection of points. You know, points are represented by (x, y). Many points are put together to form a point set. Such as {(2,4), (10, -5), (0,0), (3,4)} refers to (2,4), (10, -5), (0,0), (3,4). {(x, y)|y=3x-7} refers to the set of all points on the straight line y=3x-7. This is the content of the first chapter of compulsory mathematics in senior high school.