Apart from its use as an adjective, little can also function as a determiner, a pronoun and an adverb.
As a determiner, it precedes nouns or noun phrases, as in ‘Little progress has been made in the search for a cure for the disease’ and ‘I had a little money left so I took a taxi’. The distinction between little and a little in these examples is that the former means not much and the latter some.
As a pronoun, little can be used with or without the indefinite article with the same distinction in meaning as above, e.g. ‘They have very little, but what they have, they share’ and ‘I’d like some wine but just a little’.
Little can also be followed by of, as in 'Little of the original city wall remains standing today’ and ‘Mix in a little of the flour to make the liquid thicker’ and can itself follow the definite article, e.g. ‘The little I have read about the country does not exactly encourage me to go there’.
Examples of little and a little functioning as adverbs are: ‘These days she goes out very little' and 'He talked a little about his childhood'.
Little is also used in a few fixed expressions. Examples include little by little (meaning very gradually), as in ‘Little by little our eyes adjusted to the darkness’, and little did someone know/think/realize (used to emphasize that someone did not know/think/realize that something was true), as in 'Little did I realize when I wrote the story that millions of people around the world would read it’.