Angle measurement

Angles are formed when 2 lines meet:

There are 3 types of angles:

Angles are measured in degrees.
The symbol for degrees is a little circle next to the angle's size, like this: 30^o.
A right angle is 90 degrees, or 90^o

A straight line contains 2 right angles, so it is 180^o:

Here are a few typical angles: