Take a look at some basic geometric objects: line, ray, point, etc.
Play with these geometric objects. Notice how they move. Scroll down for written descriptions (definitions) of the objects.
We may think of a point as a "dot" on a piece of paper. A point has no width or length. A point specifies a location on your paper.
A line is a collection of points strung together. A line always extends forever in both directions.
A ray is a line that has a beginning, but no ending. Think of a ray as a line that shoots in one direction forever.
A line segment is a line that has a beginning and an ending. It does not extend in either direction forever.
Two segments, rays, or lines that intersect form an angle. The point where the lines intersect is called the vertex of the angle. The two rays, segments, or lines are called the sides of the angle.