The words beat, beet sound the same but have different meanings and spellings. Why do beat, beet sound the same even though they are completely different words?
The answer is simple: beat, beet are homophones of the English language.
To strike repeatedly.
To subject to repeated beatings or physical abuse; batter.
To punish by hitting or whipping; flog.
To strike against repeatedly and with force; pound: waves beating the shore.
A biennial Eurasian plant (Beta vulgaris) grown as a crop plant for its edible roots and leaves.
The swollen root of this plant eaten as a vegetable, typically having reddish flesh.
The sugar beet.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition and Wordnik.
Homophones (literally "same sound") are usually defined as words that share the same pronunciation, regardless of how they are spelled.
If they are spelled the same then they are also homographs (and homonyms); if they are spelled differently then they are also heterographs (literally "different writing").