1 We use few with plural nouns, and little with singular (uncountable) nouns. Compare:

Few politicians are really honest. I have little interest in politics.

2 There is a difference between a few and few, and between a little and little. Few and little are rather negative: they mean ‘not much/many’. A few and a little are more positive: their meaning is more like ‘some’. Compare:

His ideas are very difficult, and few people understand them.

(= not many people; hardly any people)

His ideas are very difficult, but a few people understand them.

(= some people better than nothing)

Cactuses need little water. Give the roses a little water every day.

3 Few and little (without a) are rather formal. In conversation, we prefer not many, not much, only a few or only a little.

Only a few people speak a foreign language perfectly. Come on! We haven’t got much time!