The words team, teem sound the same but have different meanings and spellings. Why do team, teem sound the same even though they are completely different words?
The answer is simple: team, teem are homophones of the English language.
Obsolete Offspring; lineage.
Sports & Games A group on the same side, as in a game.
A group organized to work together: a team of engineers.
Two or more draft animals used to pull a vehicle or farm implement.
To be full of things; abound or swarm: A drop of water teems with microorganisms.
Obsolete To be or become pregnant; bear young.
Archaic To give birth to.
To pour out or empty: teemed the molten ore into a huge mold.
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").