Kurses are spells cast on one person by another, which have short or long-lasting effects, however all can be cured by a simple counter-spell.
In contrast, a Curse is the worst possible result of a meeting with the gods.
A Curse is a negative effect (compare with a Blessing) which lasts for ten generations from the original Cursee. Any children had by the tenth generation (should the family last that long) will no longer be Cursed
Each of the gods has their own specific Curse. Slor, for instance, is known for his trademark Curse of shrinking anyone who teases a dwarf (for their short stature) to the size of a fairy, regardless of their original height. So far, no fairy has ever been Cursed this way.
A Curse cannot be reversed by any other god than the original Curser, and even this is only very, very rarely done.