Collinear as the word symbolises 
"Co" means Together and
"Linear" means on the line.
So, Collinear Points are those points which falls on the same line.
Below diagram represent, Collinear Points A, B & C.
In the above Diagram, Points A, B and C falls on the same line and
Hence they are called Collinear Points.
Difference between collinear and noncollinear points

