The words packs, pax sound the same but have different meanings and spellings. Why do packs, pax sound the same even though they are completely different words?
The answer is simple: packs, pax are homophones of the English language.
Third-person singular simple present indicative form of pack.
Plural form of pack.
Ecclesiastical A small flat tablet adorned with a sacred image that worshippers kiss when offered the kiss of peace.
Ecclesiastical The kiss of peace.
A time of wide-ranging stability when there is only a single dominant power. Used with a Latinized name: "Editorials lauding the civilizing influence of Pax Britannica were met with ... a crushing disinterest from most of the public” ( Nisid Hajari).
Definitions from Wiktionary, Creative Commons Attribution/Share-Alike License, 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").