These are how I personally view these terms and use them on my blog, though you’ll find a lot of other witches use them the same ways I do.
Spell:
Spells differ from other methods of magic because they can be so versatile and can have so many different effects. Essentially using your power to influence, change, or accomplish a goal would be considered a spell. Spells can have many components or none at all and can be traditional or new. Some spells suggest you cast circles before performing them and others do not. Some call for specific placements of altars or herbs and some are spontaneous and chaotic. Both forms of spellwork are valid because ultimately we’re just trying to achieve a result.
Charm:
Charms are physical objects made for a specific purpose that must be left in specific places to carry out their intentions. For example if you make a charm to ward off nightmares you would keep it above your bed. The difference between charm and enchantment is that when you have a charm you’ve made it for a specific purpose. You make a necklace to ward off worrying. You make a satchel, or a cake, or a painting and therefore it is a charm.
Enchantment:
An enchantment is an object that already exists and performing magic on it for a purpose. You would enchant a necklace to help ward against worrying. You would enchant your shoes to help you run faster. You would enchant your lip gloss to help you speak clearer and be more charismatic.
Curse:
A curse is a spell that is casted with negative intentions or outcomes for the target. There are no rules as to why curses should be cast, nor “real reasons” for them. Some people feel curses aren’t for them and that is perfectly acceptable. Some people feel like cursing people for no reason and that is also perfectly acceptable. Cursing itself has no ties to 3 folds, laws of returns or anything of that nature. Those specific beliefs are not curse related, they are typically though not always either Wiccan, or Neo Wiccan beliefs.
Hex:
A hex is similar to a curse as it is a spell with negative intentions on a person. However a hex grows and develops and binds closer to its intended target when certain actions are performed. For example you may hex someone speaking ill of you. Every time they do a negative effect would take place and with increased frequency the hex would become stronger and more powerful.