I did consular processing when I got my Green Card. It's the FINAL step fo the GC process. You don't need to be outside the US for all the other stages, in fact I think if you leave during some parts, it would be considered abandoning your application. It just means that while you're in the US, you need to schedule an appointment at the US embassy/consulate in your home country, and fly back. Then you go through the appointment and there on the spot you're approved or rejected. It's a big nerve wracking but unless you lied you will be fine. Then you fly back to the US.

For me CP was much much faster, on the order of months.