We use adjectives to describe how something is/looks. For example: The door is green and big. The question is: What is the door like?
Adverbs are used to describe the verb and usually have a "ly" at the end. For example: The child walks slowly. The question is: How does the child walk?
There are also some irregular adverbs:
Good -> Well
Fast -> Fast
Hard -> Hard
Late -> Late
Early -> Early
Lively -> Lively
Far -> Far