What are right, acute, obtuse, and reflex angles?

A right angle is an angle that measures 90˚ (degrees). It is also known as a ‘quarter turn’ because it is a quarter of a full turn, which measures 360˚. A right angle is represented by a small square inside the angle.
An acute angle is one that measures LESS than 90˚.
An obtuse angle is one that measures between 90˚ and 180˚.
A reflex angle is an angle that measures between 180˚ and 360˚.

Draw an angle with the help of a protractor

Construct an angle with the help of a compass and a ruler

Angle Bisector

An angle bisector is defined as a ray, segment, or line that divides a given angle into two angles of equal measures. The word bisector or bisection means dividing one thing into two equal parts.

The angle bisector in geometry is the ray, line, or segment which divides a given angle into two equal parts.

For example, an angle bisector of a 60-degree angle will divide it into two angles of 30 degrees each. In other words, it divides an angle into two smaller congruent angles. 

Divide an angle into two equal angles and 4 equal angles