Question

what is an angle?

Answer 1

the space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet

Answer 2

here is an example

Answer 3

An angle measures the amount of turn
There are many different types of angles:
Acute
Straight
Right
and Obtuse:

There is also a reflex and Full rotation:

For a better understanding of Angles you can go to:
http://www.mathsisfun.com/angles.html