Adjectives are words that describe nouns (people, objects, animals, feelings, etc.). Adjectives give a better idea of how a noun is.
For example:
A girl // A nice girl. // A nice tall girl. // A nice tall French girl.
The last sentence provides much more information about this girl.
That's because we added adjectives to the noun girl.
Adjectives in English go before nouns.
Another important thing to remember about adjectives is that they do not have a plural form.
E.g.: A nice girl. and Two nice girls.