Adjectives qualify a noun while adverbs modify verbs. In fact, the word "adverb" means "next to a verb" in latin.
Many adverbs derive from adjectives. Most of them are formed by adding the suffix -ly to the adjective. The adjectives ending in -ble just drop the final -e and add -y, while those adjectives that end in -y drop it and add -ily. Some examples are:
*We shouldn't confuse the words hard and hardly. They are both adverbs but have different meanings: hard means rough or difficult, whereas hardly means barely or not much. Can you see the difference between "working hard" and "hardly working"?
Watch this presentation and do the exercises below: