A little:
Means some/a small amount of.
Used with uncountable nouns.
Example:
He spoke (only) a little English. (some English)
He spoke (very) little English. (hardly any English)
A few:
Means some/a small number of.
Used with countable nouns.
Example:
She has (very) few problems. (not a lot of problems)
She has
(only) a few problems. (some problems)