Fatty acids are merely carboxylic acids with long hydrocarbon chains. The hydrocarbon chains length may vary from 10-30 carbons (mostly 12-18). The non-polar hydrocarbon alkaline chain is an important counterbalance to the polar acid functional group.
In acids with only a few carbons, the acid functional group dominates and gives the whole molecule a polar character. However, in fatty acids, the non-polar hydrocarbon chain gives the molecule a non polar character.