The words sewer, suer sound the same but have different meanings and spellings. Why do sewer, suer sound the same even though they are completely different words?
The answer is simple: sewer, suer are homophones of the English language.
An artificial, usually underground conduit for carrying off sewage or rainwater.
A medieval servant who supervised the serving of meals.
One that sews: a sewer of fine clothing.
One who sues; a suitor.
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.