Participles are verb forms that can function as adjectives in a sentence. They come in two forms: present participles (ending in -ing) and past participles (often ending in -ed, -en, -d, -t, -n). They modify nouns and pronouns, adding more information about them. For example, in the sentence "The running man is fast," "running" is a present participle modifying "man." To use participles effectively, ensure they agree with the nouns they modify and are correctly placed in the sentence.