What's the difference between radians and degrees?

Radians: a unit of angle, equal to an angle at the center of a circle whose arc is equal in length to the radius.

Degrees: a unit of measurement of angles, one three-hundred-and-sixtieth of the circumference of a circle.

Radians is baced on the equation: 2×pi×r=pi×d

and pi=180° 2pi=360°