Project Magenta is THE essential software package you'll need for your cockpit. It is somewhat expensive, but you do get what you pay for! There are some free alternatives, but none are finished. Nor do they give the same fidelity and functionality.
Let's take a closer look:
Left: Primary Flight Display (PFD), where you'll get information on the horisontal and vertical situation. Among other things.
Right: Navigation Display (ND), where you'll find your route, navigation data and other useful information.
Left: Engine Indicator and Crew Alerting System (EICAS), where a lot of information can be displayed. Primary, you'll see engine indicators on two of these display, located at the center of the main instrument panel (MIP); One on the MIP itself, another just below it in the "FMC bay" (just in front of the control stand / Throttle Quadrant).
Right: Flight Management Computer (FMC - also known as CDU). The thingy you will use most in your cockpit. Here you type in all vital data for the flight, including the waypoints and so on.
These programs does run on just one computer, but it is no "flight in the park". You will need to run these programs over several computers in a network if you want smooth instrument displays (and no delays).¨
PMSystems is another program from Project Magenta. It simulates the system logics (mostly located at the overhead panels). You do not need PMSystems in order to have a functional cockpit - but if you are going to build an overhead panel, you should buy PMSystems - and watch the overhead come to life!
I have just recently purchased the Project Magenta suite, so I do not have any more to fill in here. But I do recommend that new simbuilders do purchase Project Magenta first. Before anything else! That way, you will be able to "do some legs" (meaning that you can fly around the world during your build-time). If you do not follow the "fly and build" -idea, you might end up spending a couple of thousand $$$ and loose the interest. Bad idea! Most builders recommend PM-MIP-Glare-Pedestal-Overhead. I am going to walk this road: PM-Overhead-Glare-MIP (and so on - I haven't decided further yet).
If you know the PMDG 737, Project Magenta will be easy to master. It is essentially the PMDG panels - but you can tweak, interface and do whatever you want with it.