The words lase, lays, laze, leas, leis, leys sound the same but have different meanings and spellings. Why do lase, lays, laze, leas, leis, leys sound the same even though they are completely different words?
The answer is simple: lase, lays, laze, leas, leis, leys are homophones of the English language.
To function as a laser; emit coherent radiation by the action of a laser.
To subject to laser light: lased the tissue during surgery.
To direct a laser used to guide munitions at (a target).
Plural form of lay.
Third-person singular simple present indicative form of lay.
To be lazy; loaf: laze around the house.
To spend (time) loafing: lazed the afternoon away in a hammock.
Plural form of lea.
Plural form of lei.
Plural form of ley.
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").