Answer:
Words that have the same spelling but different meanings are called homonyms. Examples are beat (rhythm) and beat (to whip, as eggs). But this term is also (confusingly) used for words that simply have the same sound (pronunciation), such as eight and ate. These are homophones (sound alike words).
If they have the same spelling, but different pronunciations, they are homographs. (written the same) such as sow (female pig) and sow (to seed), or the tenses read (pronounced reed) and read (pronounced red). Homographs require a context clue to determine how they are pronounced.
There are a great number of homophones in English.
(see the related question for examples)