To quantify means to measure the amount or number of something. Accordingly, quantifiers indicate the amount or number of a noun phrase.
There are various types of quantifiers. It is important to know when to use the one or the other.
MUCH is used for uncountable nouns (e.g. water, milk, time, money) whereas MANY is used for countable nouns (e.g. glasses of water, bottles of milk, hours, dollars).
How many students came to the party yesterday?
How much time do we have left to complete this exercise?
Similar to much and many, LITTLE is used for uncountable nouns (e.g. energy, money, time) whereas FEW is used for countable nouns (e.g. friends, minutes, countries).
There are few pupils in this class today.
Unfortunately, Susan has only had few opportunities to practice speaking English.
Peter takes little care of his younger brother, even though his mother urges him to care more.
I am sorry, but I have only understood little of what you said.
A LITTLE is used for uncountable nouns (e.g. time, wine, love) whereas A FEW is used for countable nouns (e.g. years, people, chairs).
In a few years he will be president.
Don't take it too personally. I simply need a little time for myself.
The German translation helps understanding the slight differences in meaning.
LESS is the comparative of little and is, therefore, used for uncountable nouns (e.g. work, money, sleep). In contrast to that, FEWER is the comparative of few and is used for countable nouns (e.g. opportunities, problems, times).
Fortunately, Simon has less work than last month.
There are fewer applicants for this job than last year.