The word "Hex" derives from the German word for "Witch" (Hexe), but it is commonly used in the English language to indicate an evil or malevolent spell.
So in English, a Hex is a malicious, harmful, spell. A curse relies on the power of the individual who casts it; a Hex follows the same format as a spell. And although "anyone can cast a hexing spell, many people believe that Hexes cast by a witch are more powerful than those cast by a lay person.
This may or not be true; depending on the individual casting the Hex. Intent is the key with Hexes: identical material and techniques may be used to cast or break a Hex.
Identical spells may be used to cast a malicious Hex or create "loving" magic. An example would be tossing "graveyard" dirt at someone may be intended to stimulate disaster "or" create an Aura of protection. The actions and materials may be identical; the sole difference is the focus and the "intent" of the spell-caster. The focus and the intent is enough to produce the desired outcome.
Good Luck, Good Love and Good Magic,