Coordinates can be one or more numbers.
If a coordinate is one number it defines the position of a point on a line.
Below are three examples:
Here 0 defines the position of a point on a line.
0 is also called the origin because it is where coordinates are measured from.
Here is the point at position 2. It is 2 from the origin.
Coordinates use negative numbers as well. Here -3 denotes the position.