Euler rotation

i am trying to rotate the object in blender using python coding i want to know 2 thing:
1)what is the difference b/w XYZ,ZYX,ZXY,YZX,YXZ,XZY Euler. which one i should use?
2) how do i change these using python coding?

import bpy
import mathutils['Suzanne'].rotation_mode='XYZ'
eul2 = mathutils.Euler((Roll, Pitch, Yaw), 'YXZ')['Suzanne'].rotation_euler=eul2

sorry i am using bge… not bpy