(A) few, (a) little, what difference?

(A) few

Let’s say it in a few words… A few + plural noun means "a small number of/a handful of", and has a positive connotation to it.
Example: "Have a few biscuits, my darling" (positive perspective).

However, few + plural noun means "not a lot of, not much of" something, and therefore has a negative connotation to it.
Example: "There are few biscuits left for you, my darling, I’m afraid" (negative, the speaker stresses the lack/absence of it).

(A) little

Similarly, a little + singular noun means "a small quantity/a handful of something", but with quite a positive connotation.
Example: "There’s a little food left for you, my darling" (i.e. it is a small quantity but it is something nice that you can have, and you’ll like it).

However, little + singular noun also means "a small quantity of" but introduces a negative perspective.
It stresses the lack or scarcity of something, as in "There’s little food left for you, I’m afraid… Almost everything was eaten" (i.e. you should go to the nearest store and buy some food for yourself).
Another example: "We still have a little time to eat something before the train leaves" (un peu de temps, i.e. a positive perspective) VS "we only have little time to eat something before the train leaves" (peu de temps, with a more negative/pessimistic connotation).