A quantifier is a word that normally comes before a noun to convey the quantity of an object, such as a drop of milk. The majority of quantifiers are followed by a noun, however, when we know what we're talking about, we may use them without it.
Let us take an example,
Do want some water? - Yes, just a little.
Here little indicates that a person wants little water.
there are various types of quantifiers such as to describe large amount ( a lot, many) and to describe less amount ( few, less, little) and there are some undefined quantities as well like (any, some).
Also, some quantifiers have the almost same meaning but they are used differently like one will be used with countable nouns and another one with an uncountable noun.