The pronoun “I” is subjective, meaning it is always used as the subject of the sentence or clause. The pronoun “me” is objective; it is used to receive action from the subject or to be the object of a preposition.

It is important to know the eight parts of speech to craft intelligent, and intelligible, sentences. You use them all the time, but if you forget the difference between an adjective and adverb, you wind up coining new usages and infuriating copy editors.