Prefixes and suffixes are used to modify the meaning and structure of words. Prefixes typically change the meaning, while suffixes often alter the grammar or part of speech. Some common suffixes in English include -er, -or, -ing, and -ed, which can form nouns, adjectives, and verbs. Word roots often come from Latin and Greek and combining them with prefixes and suffixes allows new words to be created in a systematic way to express new concepts in English.