Change in wages or salaries causes increase (expansion) or decrease (contraction) in 'quantity supplied' of labor, which leads to movement along the curve.
Change in any factor other than wages or salaries cause increase or decrease in 'supply' of labor, which leads to shift of the curve.
These factors other than wages can be :
- Workers taste & preferences, desirability related to job : Favourable change in taste & preferences increasing desirability of that job increases the labor supply & shifts the curve rightwards. Unfavourable change in taste & preferences decreasing desirability of that job decreases the labor supply & shifts the curve leftwards.
- Government norms related to training of a job : Good changes in training norms increases supply & shift the labor curve rightwards, bad change in training norms decreases supply & shifts the labor supply curve leftwards.