That's an interesting question! At first I thought they were pretty similar, but I had a think about this, and there are several key differences:
* With loot boxes, you can often trade the items that you won
* Loot boxes often show you the rarity (and sometimes the value) of an item that you've won.
* Loot boxes often show a spinning wheel or similar device that adds a level of excitement and a feeling of a "near miss" by showing the wheel "almost" land on an item.
* Some loot boxes allow you to "roll again" if you're not happy with the item you received.
* Loot boxes play sounds and show effects depending on the rarity of the item won.
* Loot boxes are given out for free, but you have to buy a "key" to open them.
* Games with loot boxes emphasize items that can be won from them, and encourage players to display these items for in-game prestige.
* Some loot box items give you an in-game advantage.
* Loot boxes are not edible.