The words soot, suit sound the same but have different meanings and spellings. Why do soot, suit sound the same even though they are completely different words?
The answer is simple: soot, suit are homophones of the English language.
The fine black particles, chiefly composed of carbon, produced by incomplete combustion of coal, oil, wood, or other fuels.
A set of matching outer garments, especially one consisting of a coat with trousers or a skirt.
A costume for a special activity: a diving suit; a running suit.
A group of things used together; a set or collection: a suit of sails; a suit of tools.
Games Any of the four sets of 13 playing cards (clubs, diamonds, hearts, and spades) in a standard deck, the members of which bear the same marks.
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").