The words laser, lazar, lazer sound the same but have different meanings and spellings. Why do laser, lazar, lazer sound the same even though they are completely different words?
The answer is simple: laser, lazar, lazer are homophones of the English language.
Any of several devices that emit highly amplified and coherent radiation of one or more discrete frequencies. One of the most common lasers makes use of atoms in a metastable energy state that, as they decay to a lower energy level, stimulate others to decay, resulting in a cascade of emitted radiation.
Archaic A diseased person; a leper.
Common misspelling of laser.
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").