Bed-in-a-box is a slightly misleading term, as it refers to a mattress only, not a full bed, which is shipped to your door in a box. The term is usually used to describe a certain type of foam mattress which can be compressed, rolled, boxed, and shipped in a surprisingly small package due to savvy manufacturing and packing techniques. Other than the shipping method, there's nothing particularly different between a standard mattress and a bed-in-a-box.