Obviously it has a simple explanation but, as a rookie in the business, i would like to hear something about it. That's because i only have carrara 4 pro and hexagon. Can we also do great renderings with only these 3d programs?

The renderer of Carrara is considered to be one of the industries best by a lot of people, for speed and the end result. The better and more beautifull and real you want your image to be, the longer your render times will be. The network rendering you get for free is to compensate for that probably. There is no subsurface scattering or translucency in C4Pro (yet) but all other funky things you hear people about regarding stand-alone renders or expensive plug-ins. Some of the names are different, but Global Illumination, Indirect Light, Sky Light, HDRI, caustics, soft shadows, blurred shadows, blurred reflections, motion blur and even rendertime displacement (if you have Anything Grooves) give you all posibilities you need (rookie or not). And you have to know that great renderings also depend on great shaders and great lighting. Knowing how photographers ligh their photos, for instance, is knowledge that can greatly enhance your work. There are people that use Carrara solely for rendering, so that must say something too. Good luck with finding out!

How good your renders are doesn't simply depend on the software you use; it depends on how good a craftsman you are. Learn to use Carrara to its limits and you'll be able to turn out renders that look as good as most of the best out there. There are probably a lot of people who shell out a lot of money for 'the best' but who don't put in the time (or haven't the talent) to get a good result. And it's worth remembering that when you look at a render you've not really any idea how much postwork was used, whether render passes were used to fake effects, compositing or other image manipulation techniques employed. It's all legitimate (it's all a 'fake' anyway) but it makes it very difficult to assess particular software. If you're REALLY keen to learn about rendering, I recommend 'digital Lighting & Rendering' by Jeremy Birn, published by New Riders. And by the way, AGrooves does NOT do rendertime displacement, it creates geometry before render.