Calcitic Lime is used to raise the soil pH and to provide a high level of benefical calcium to the soil.
Lime should always be applied based on a soil test. Applying too much lime can raise the soil pH to high, which could then tie up valuable nutrients in the soil and lead to increase plant stress or plant chlorosis (yellowing of the leaves). It is much more difficult to lower soil pH than to raise it, so always use lime judiciously.