A data core is a blank storage core: a processor sealed in glass, made in a Fabricator. A Lab prints copies of a design onto data cores. A copy lets whoever holds it build that design once, even when its blueprint is locked behind research or the design has been retired. The build uses up the copy, and its cores become slag.
A copy weighs as much as the cores it was printed on, and is traded, carried and dumped like any other item.