It's a tool to do some cool things with Ren'Py games. You extract the RPA's and you can just view the videos/animations if they have any and the images conventionally with apps built into Windows or my preferred app XnViewMP.
This is the old version, works with almost all Ren'Py versions, you can skip if you want and use the new one, which is refered to sometimes as UNREN Ultrahack.
UnRen.bat v1.0.10 - RPA Extractor, RPYC Decompiler, Console/Developer Menu Enabler
This is the newer version.
UnRen-old, UnRen-forall(v8), UnRen-Powershell-forall(v8)
Just drop in folder, and run and then select an option.
What I mean by tab skipping, some games don't let you skip unseen text, that will enable it.