It is composed of two panels, each with 4 resource slots. You can then store 8 stacks of resource or items that attach to a single slot.
You can not attach to a storage anything that require 2 or more adjacent slots (like the wind turbine, research items, or other storages).
When attached on the side of modules, the 2 panels flatten.Vehicle Storage. Both have very different purpose, they are not the variant of the same item (as with battery for instance).