Adverbs are the words which are used to describe an action (verb) like playing well, behave nicely, rightly punished and so on.

Some adverbs are incorrectly used by many:
They worked hardly for this presentation.
The car went fastly.

Here both the adverbs ( hardly and fastly ) are incorrect.

Fastly is no word at all. So, the statement should be:
The car went fast.

Hard is the correct adverb to be used in above statement.
They worked hard for this presentation.

Hardly is the adverb which means very little, hence giving it a negative tone.
It hardly rained last summer.
He hardly goes out to meet his friends.