A mark of a position on a plane is called a point.
A point is a representation of a particular location on a plane in geometric system. It is usually denoted by a dot (.) symbol. It appears as a circle of zero radius.
The concept of point is mainly useful to identify different locations on a plane and also useful to know where exactly they are on the plane.
A point has three properties.
Every point is represented on a plane by a dot symbol graphically but it raises an issue if more points are considered on plane. In order to talk about a particular point among them, every point is denoted by a capital letter.
For example, four points are considered on them plane but all of them are represented by same dot symbol. It is easy to speak about one of them because of identical representation. So, name to each point to avoid this problem.
All four points are denoted by capital letters $A, B, C$ and $D$ and they are called $point \, A, Point \, B, Point \, C$ and $Point \, D$ respectively. Now, it is very easy to identify every point and also easy to talk about every point.