An adverb is a word that modifies a verb, an adjective or another adverb. Mostly it is similar to the adjective, but there are a few exceptions.
Most adverbs are formed by adding the -ly to the end of the adjective, for example "careful" turns into "carefully", "slow" turns into "slowly".
However some adverbs are identical to the adjectives, for example "fast" stays "fast" (fastly is wrong).
On the other hand, there are some adjectives that do end with -ly, so the word ending can not determine that the word is an adverb.
For example:
lovely - What a lovely dog.
In this tutorial we do not want to focus on how adverbs are formed, but on how the comparative and superlative of these adverbs are formed. The rules are identical to the rules of the comparative and superlative of adjectives. However adverbs modify adjectives, verbs or other adverbs but not nouns. For example, if we compare two actions (verbs), we use the comparative form. If we compare three or more actions we use the superlative form.