Also see Bags
Containers are objects that can hold other items. Your backpack and other bags are one example of a container. Container is a more general word since it also applies to storage spaces that aren't really bags, such as a quiver. The search term on the Auction House for all bags and bag-like objects is Containers.
Container can also sometimes be used to describe a game object like a treasure chest that holds items until the player loots them. One could argue, then, that an unlooted corpse is also a container. This version of the word is not used as frequently.