The words gest, jest sound the same but have different meanings and spellings. Why do gest, jest sound the same even though they are completely different words?
The answer is simple: gest, jest are homophones of the English language.
A notable adventure or exploit.
A verse romance or tale.
A prose romance.
A playful or amusing act; a prank. See Synonyms at joke.
A frolicsome or frivolous mood: spoken in jest.
An object of ridicule; a laughingstock.
A witty remark.
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").