What is the difference between harmony and consonance in music?

Question

I am new to music theory and I was wondering what the difference is between harmony and consonance/dissonance. What are the reasons behind these terms and how can you apply it in practice if, for example, you'd like to compose a song?

Answer 1

Harmony means "notes sounding together nicely." Consonance is a bit more nuanced -- it describes how nicely two notes sound together. Its antonym is dissonance -- when two notes are jarring together. You could say a chord or interval can fall on a scale from consonant to dissonant.