"A little..." will describe something small. A miniaturized version of something. For instance "We went on a little vacation this weekend." "A bit.." is a pretty open term. Bit can mean a small amount of units, a small peice of a unit, or a small unit by itself. Note that many cases the two terms will be combined to "A little bit.." and in many ways the meanings become mixed by this. People will say a little or a bit with the meaning of a little bit. "A few.." refers to a small number of things and greater than two. Generally, few is accepted to be the number three. Where as a (singular) would simply be an apple. Two would be a couple apples. Three would be a few apples. However, though few is generally accepted as a replacement for three, it will also be used as a generalization for numbers in this area, such as 4 or 5 as well.