What does that really mean?
More on straight: Lines must be straight or they would look like this.
Dots: A line is made up by so many dots that when we draw the line, we make it solid. However, keep in mind that it's just an infinite number of dots.
Showing infinity: We use arrows on the tips of the line to show that the line continues forever.
Unlike a line, a ray has one endpoint and continues forever in only one direction.
Unlike a line, a segment has two endpoints.
