What Is Blackbox or repack
Blackbox or repack is like this:
Imagine this sweet new computer just came out onto the market. Everyone wants it, and almost nobody can afford it.
So these folks from the "underground" black market, find out what parts this computer comes with, and buys them. They then get all these parts and resell them to folks, letting them assemble it themselves for far cheaper.
In essence, a "blackbox repack" is a file that's been pirated, and then shrunk down into what are called "ZIP" files for size reduction. Then, when you download them, you "unzip" them into their full games and reduce games resolution. They usually have a crack associated with them, so you can completely skip buy game licensing and legal mumbo-jumbo.
EDIT: Yes, it's totally playable. Just right click the file that you download and click "Extract All". That will unzip the file, and load the regular files onto your drive. Double click the "Application" type file, and the game should begin to run/download drivers to run.