An angle is in standard position when
initial side is always on the positive x axis, therefore the terminal side are the other ray that determine the degree of the angle.(quadrant also)
We measure angles in degrees or radians. To measure an angle, start at the initial side and go towards the terminal side.
Counter clock-wise - the angle is positive
clockwise - the angle is negative
An special note, standard position angles can go around more than 1 rotation in either direction. (over $360\degree$)
The Terminal side also determine the quadrant of the standard position angle, what quadrant it is located at, what quadrant it live in.