Ben Boldt "software instruments"

Saw a discussion recently regarding “GarageBand/Logic” software instruments by Ben Boldt, but can’t find it now.

As I recall, the discussion involved the “safety” of these things and one person said they were safe and virtually “everybody has downloaded them.” Apparently they are free.

The question is: what exactly are these? Loops? I’ve gone to the web page and seen the “boxes” but still don’t know exactly what there are. Also, what is a “mirror” download?

And what do I do with them? Just move them into the GB loops section?

Thanks.