Storage refers to storing something, like in a basement or attic. People keep all sorts of things in storage — from fur coats to bowling trophies.
When you store something, you put it away somewhere safe, so storage is the act of storing. Squirrels gather nuts and put them in storage by hiding them. A grocery store might use a stockroom for storage. If you have canned food in the basement, that's storage. Some storage is for emergencies, while other storage is for things you might want to look at another time, like old photos. Things in storage are being saved for later.