GWM Euler angles are often used to express the rotation of an object. There are at least 12 different methods of expressing them, but in each case there are just 3 angles. http://mathworld.wolfram.com/EulerAngles.html
One common system is used by aircraft, involving rotation about the vertical (heading), axis through the wings of the aircraft (pitch) and rotation about the length of the craft (roll).
Each rotation can be expressed as a matrix:
Rheading = [ cos(h) -sin(h) 0 ]
[ sin(h) cos(h) 0 ]
[ 0 0 1 ]then
Rheading *(x,y,z) results in a vector that has been rotated about the Z axis (heading if you allow Z to be vertical). for example Rh*(1,0,0) -> (cos(h), -sin(h), 0).
2 more matrices can be written for rotation about Y and X, multiplying the matrices gives a total rotation matrix for the Euler angles.