Two angles are Coterminal angles if they are drawn in the standard position (i.e. vertex of the angle is at origin and its initial side on the positive x-axis) and have terminal sides in the same location.
So the coterminal angle can be obtained by adding or subtracting n*360 degree to the measure of an angle ( n is any integer).
e.g. if we want to find the coterminal angle of 50 degree , the we can add 360 or 720 or any multiple of 360 to it.
i.e. 50 ,410 and 770 are coterminal angles.