There are several variations of the software, differentiated by the type of license you have. Each has a different set of features available. You can compare the versions.
Where it can get confusing though is that it's just a single program that is downloaded; depending what kind of license key you plug into it, it will turn into the particular version.
So if you just download it and don't put in a license key, it's the "free" version. On our website you can request a demo license, which sends you a time-limited 10 group "standard" license to try out. So the demo license is really just a standard license, having the same set of features, just that it has an expiry date on it.