What is the difference between Hexproof and a card like Canopy Cover?
The effects are different because of what you/your refers to: it refers to an object's controller.

Canopy Cover's effect is radically different from an effect that says "Enchanted creature has hexproof", but the difference only becomes important when you use it on a creature an opponent controls.

Let's suppose you're a Green player facing a Blue player.

Enchanting your opponent's creature with Hexproof means you can't target it

Doing so means the creature now has a static ability that says:


  This permanent can't be the target of spells or abilities your opponents control.


The "your" here refers to that creature's controller - Blue player - so now Blue player's opponents can't target that creature with spells or abilities. That's you, Green player. You now cannot target that creature with spells or abilities.

Enchanting your opponent's creature with Canopy Cover means they can't target it

Doing so means the enchantment says:


  Enchanted creature can't be the target of spells or abilities your opponents control.


Since you are the enchantment's controller, the "your" in this case refers to you, the Green player. So your opponents can't target that creature with spells or abilities - that's the Blue player.