Radians
Angles can be measured in Degrees or Radians.
One Radian is 180/π degrees, or about 57.296°
A Radian is:
the angle made by taking the radius and wrapping it along the edge of the circle:
So, a Radian "cuts out" a length of a circle's circumference equal to the radius. 

There are 2π radians in a full circle 
In other words, if you cut up pieces of string exactly the length from the center of a circle to its edge, how many pieces would you need to go around the edge of the circle?
Answer: 2π, or about 6.28 pieces of string. 
Radians Preferred by Mathematicians
Because the radian is based on the pure idea of "the radius being laid along the circumference", it gives simple and natural results to many anglerelated mathematics.
For example, look at the sine function for very small values:
x
(Radians) 
sin(x) 
sin(x)/x 
1 
0.8414710 
0.8414710 
0.1 
0.0998334 
0.9983342 
0.01 
0.0099998 
0.9999833 
0.001 
0.0009999998 
0.9999998 
For very small values. "x" and "sin(x)" are almost the same!
There will be other examples like that as you learn more about mathematics.
Conclusion
So, degrees are easier to use in everyday work, but radians are much better for mathematics.
