PPSSPP is written in C++, and translates PSP CPU instructions directly into optimized x86, x64 and (soon) ARM machine code, using an efficient JIT compiler.
PPSSPP can thus run on quite low-spec hardware, including stronger Android phones and tablets, as long as there's support for OpenGL ES 2.0.
Many fixes, more games playable
Progress has been rapid, much thanks to several new contributors! As usual, see the downloads page for the new version, and look at the compatibility list.