Zheng Yan (正岩） means it's (supposedly) from within the so-called scenic area, i.e.,. the central protected area.
for a more detailed explanation of the 3 common categories.
I don't believe it says anything about what actual varietal or what generation from the original bush it is.
I would take vendor claims about tea being zheng yan or being second or third generation Da Hong Pao with a big grain of salt.