There are (degrees) in a complete revolution (i.e. a full circle)
There are in half a revolution (i.e. a straight angle, aka straight angle)
There are in a quarter revolution (i.e. 2 lines perpendicular, aka a right angle). This has a special symbol:
Angles between and are called acute angles.
Angles between and are called obtuse angles.
Angles between and are called reflex angles.
When determining whether an angle is acute/obtuse/reflex, the position of the angle isn’t important, only the size. It does depend on which angle you’re talking about though, because the opposite side of an acute angle is going to be a reflex angle!