The eight parts of speech are verbs, nouns, pronouns, adjectives, adverbs, prepositions, conjunctions, and interjections.
Verbs show action or state of being.
Nouns are the names of persons, places or things.
Pronouns take the place of nouns.
Adjectives modify nouns or pronouns and tell which, whose, what kind, and how many.
Adverbs modify verbs, adjectives, and other adverbs and tell how, when, where, and how much.
Prepositions must have an object and show a relationship between its object and some other word in the sentence.
Conjunctions join words, phrases, and clauses.
Interjections show feeling and are punctuated with either a comma or an exclamation point.
If you need further clarification on any of the parts of speech, see the Daily Grammar archives (http://www.dailygrammar.com/archive.html). Remember that what part of speech a word is depends on how it is used in the sentence.