Open Source Content Management

Hi brilliant ones

Can anyone please in layman's terms explain the difference between the above. Furthermore, I have what I think is a good idea for one of the above which would be very beneficial to large volumes of people in SA (has to do with the cellular industry), but do not have a clue as to where to start. Has anyone gone through this? What were your steps? Where do I find a developer (reliable/honest/cheap)? Any advice and guidance will be greatly appreciated.