The words scold, skald sound the same but have different meanings and spellings. Why do scold, skald sound the same even though they are completely different words?
The answer is simple: scold, skald are homophones of the English language.
To reprimand or criticize harshly and usually angrily.
To reprove or criticize openly.
One who persistently nags or criticizes: "As a critic gets older, he or she usually grows more tetchy and . . . may even become a big-league scold” ( James Wolcott).
A medieval Scandinavian poet, especially one writing in the Viking age.
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").