It's a program where select groups have a dedicated hiring path to United. In the program you get the Hogan automatically, then if you pass that you can schedule an interview. If successful in the interview you are in a pool to start at United in seniority order.

There are a few different groups who have a CPP.

Regional Airlines - ExpressJet, Air Whickey, Mesa, and Commutair
Metro State University
Lufthansa Fight school