Homonyms generally include two categories of word types: homophones and homographs.
Homographs are words that are spelled the same but have different meanings.
Homophones are words that have exactly the same sound (pronunciation) but different meanings and (usually) different spelling.
For example, the following two words have the same sound, but different meanings and spelling:
hour and our
In the next example, the two words have the same sound and spelling, but different meanings:
bear (the animal)
bear (to carry)
Usually, homophones are in groups of two (our, hour), but very occasionally they can be in groups of three (to, too, two) or even four. If we take our “bear” example, we can add another word to the group: