Collinear point are the point which lie on the same straight line.
Let us take an example of the sitting arrangements of students in a classroom.
The students sitting in a desk in a row are collinear. Let us suppose that 3 students sit in a desk in horizontal direction then these represent collinear points. Students 1, 2 and 3 are collinear points.
Similarly, , students 1, 4 and 5 in the column are collinear points.
Please see the attached image to understand this.