Labor includes all forms of work. Such work often requires skills. Skills are enhanced with accumulation of human capital which consists of education, training, good health and mobility. The compensation or price for labor is known as wage.
All forms of human endeavor require attention and effort. One may only hope that the work one has, is also pleasurable, but it is work nevertheless. That is why it is call labor. It is applicable to a ditch digger, as well as to a scientist, accountant, musician or artist.