Adjectives and adverbs are parts of speech commonly called modifiers. An adjective modifies (or describes) a noun or pronoun, and an adverb modifies (or describes) a verb, adjective, or another adverb.
Some adjectives and adverbs require memorizing a few rules. For example, bad is always used as an adjective, while badly is an adverb. Adjectives and adverbs can also be used to show comparative or superlative degree. By adding ‐er you can compare two people, things, or an action; or by adding ‐est you can compare more than two things.
Effective writing requires correct spelling, and compound adjectives and adverbs can cause spelling problems. Computer spell‐check functions aren't foolproof! There are many rules and exceptions, so keep a dictionary handy to check spelling, and be consistent throughout your paper.