The endpoint of two rays is the common point where both rays meet. This point is known as the vertex. The two rays extend infinitely from this point in opposite directions forming an angle. The vertex is crucial for defining and measuring angles in geometry.

In this chapter students learn about lines and angles. A line extends infinitely in both directions while an angle is formed when two rays meet at a common endpoint called the vertex. Types of angles include acute right obtuse and straight. Understanding these concepts helps in solving geometric problems.