Adverbs can tell you where, when, how, why and to what extent something happens.

There are several different classes of adverb (see above).

They are often formed from adjectives or nouns by adding the suffix -ly.

For example: Quick becomes quickly, sudden becomes suddenly, intelligent becomes intelligently.

To form an adverb from adjectives ending in -y change the y to i before adding the -ly.

For example: angry becomes angrily, busy becomes busily.

To form an adverb from adjectives ending in -e drop the -e before adding the -ly.

For example: feeble becomes feebly, true becomes truly.

Some adjectives ending in -ly need no changes.

For example: heavenly.

However there are exceptions.

For example: sly becomes slyly, shy becomes shyly.

Some adverbs do not end in -ly.

For example: fast, hard, straight.

Adjective Pretty Serious Fast Quiet
Example She was a pretty girl. He was a serious boy. It was a fast car. They were quiet children.
Adverb Prettily Seriously Fast Quietly
Example The bird sang prettily. The policeman spoke seriously. Schumacher drives fast. The woman spoke quietly.

Adverbs can modify adjectives

An adjective can be modified by an adverb, which precedes the adjective.

For example:-

That's really nice.

Adverbs can modify adverbs

Some adverbs can modify others. As with adjectives, the adverb precedes the one it is modifying.

For example:-

She did it really well.

Adverbs can modify nouns

Adverbs can modify nouns to indicate time or place.

For example:-

The concert tomorrow.

The room upstairs.

Adverbs can modify noun phrases

Some adverbs of degree such as quite, rather, so, such ... can modify noun phrases.

For example:-

We had quite a good time.

They're such good friends.

Adverbs can modify determiners, numerals and pronouns

Adverbs such as almost, nearly, hardly, about, etc., can be used:

For example:-

Nearly everyone, who was invited, came to the party.

Adverbs can modify sentences

Some adverbs modify a whole sentence, not just a part of one.

For example:-

Luckily the car stopped in time. In this sentence luckily modifies the whole sentence, it shows that it was good luck that the car stopped in time.