Homonyms are two or more words that sound alike or are spelled alike but have different meanings. There are three types of homonyms: those that are spelled alike and sound alike, those that sound alike but are spelled differently and those that look alike but do not sound the same.
An example of the first type of homonym above is the word "bank." "Bank" can mean slope, such as the land leading down to a river, or "bank" can be a place where money is kept.
An example of the second type, also known as homophones, is the word pair "colonel" and "kernel." These two words are pronounced the same but spelled differently and have different meanings. "Colonel" is a rank in the army, while "kernel" is a small piece of corn.
The third type, homographs, is shown in the word "bow." "Bow" as a verb means to lower one's head as in prayer. A "bow" as a noun is something that is tied.