Hi, Engy. Warehouses are used specifically for commercial reasons - that is, they are used by businesses, and are therefore usually very big buildings. For example, a business may store the things it will sell in a warehouse. On the other hand, a storage space can be of varying sizes. Typically, however, it refers to a places where you put your personal things. For example, if you have too many things in your house, you can put it into storage.