The words silence, silents sound the same but have different meanings and spellings. Why do silence, silents sound the same even though they are completely different words?
The answer is simple: silence, silents are homophones of the English language.
The condition or quality of being or keeping still and silent.
The absence of sound; stillness.
A period of time without speech or noise.
Refusal or failure to speak out.
Plural form of silent.
Definitions from The American Heritage® Dictionary of the English Language, 4th Edition, from Wiktionary, Creative Commons Attribution/Share-Alike License 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").