Pitch is the angle around a horizontal axis parallel to the wings, thus the nose and tail both pitch up or down.
Roll is the angle around an axis drawn through the body of the vehicle from tail to nose.
Yaw is the angle around a vertical axis orthogonal to the other two above. If an airplane model placed on a flat surface is spun or pivoted around the center of mass (coordinate origin) it would be described at yawing.
Aerospace engineers develop control laws and control systems to allow pilots to control their aircraft in the three dimensions described above.