Collinear is when you have three or more points on a straight line. Points A,B, and C are collinear.
Technically a line is a group of points on a straight line. A line segment is different than a line because it has endpoints compared to a line that does not have endpoints, and extends in both directions infinitely. Check out the video to the left for a visual picture of a line.
A point marks an exact location. In Geometry class we usually mark a point by making a dot with our pencil, but in reality a point has no size. The point does not have any size or dimensions because it marks a place, and is not an object.
Points are named using an upper case letter.
You also can use lower case letters to name a line. For example:
Once you have points labeled it makes naming a line simple.