what does retail packaging mean?

Answer 1

in the world of computer components, "retail packaging" means it includes the documentation and mounting hardware while "OEM packaging" means you get just the item [and, presumably, either know or access the rest from company's website or other source].  -- grampa    [Example:  the retail package for a cpu might include a cpu cooler and thermal grease while the OEM packaging will not.  More serious box builders don't use the retail cooler anyway and thermal grease will come with their aftermarket (better) cooler.]

Answer 2

It means: the packaging of items that are intended for sale in shops, stores.