Concentrated solar is measured in suns. So if I use a mirror or a lens of 2 m^2 area and direct this light on on a 1m^2 solar panel, people talk of in this case two suns reaching the solar panel. The panel still has a similar efficiency, but double the power output due to more light shining on it. I simplified a bit but thats the idea.

Type "concentrated solar" into an image search engine, it's fascinating!