Not an unreasonable question.
The Out + Power is simply an output that includes a "Bias T". This allows feeding DC voltages back through the splitter to feed an inline amplifier, like Kandrey says. The DC voltage is allowed to pass through to the "input" side but not to the other outputs. It usually requires a separate power injector that will have a DC power feed as well as an input and output connection for RF.
Return path is often used in cable TV "broadband" service where the lower frequencies are allowed through the splitter going in the opposite direction. Usually this return path is below 5MHz. The internet broadband is run down in the lower frequencies, below 5MHz, while the RF cable TV signal is above the 5MHz point.
Return path is a separate function from the DC path. You don't need a return path for scanner use, but you might want the DC path if you ever want to run a preamplifier.
