The word coarse (with an “a”) is pronounced exactly the same as course (with a “u”), but isn’t as common.
We use the word coarse to describe something made up of large pieces. Something made from small pieces is described as being fine.
You might even describe somebody’s hair as being coarse (if the hairs are thick) or fine (if the hairs are thin). I personally have coarse, or thick, hair. I inherited that from my mother’s side of the family.
Coarse can also be used to describe somebody who lacks manners, or swears a lot. “I can’t believe the way your brother behaves at the table. He’s so coarse!”
We occasionally use coarse to describe a sound that is unpleasant and rough. “After smoking thirty a day since he was a teenager, his voice had become rather coarse.” We might also say that such a sound is harsh or grating.
Finally, coarse fishing is a mostly British term that means fishing in freshwater (not sea water) for fish that you won’t eat, should you be lucky enough to catch any. You just put the fish back in the water.
Next up: fine.