Activation prevents software piracy by verifying the product key provided by the user on the Cryptlex servers ensuring only registered product keys are allowed and also prevents reuse of the same product key on different machines.
When a user activates your product using a product key, the hardware on which the product key is used gets registered for the key. If your plan allows for 5000 activations, it means you can manage the activation, re-activation and deactivation of your product on 5000 different machines using Cryptlex.
Hardware id's (machine fingerprints) are OS specific. If a user has installed Windows, Mac OS X and Linux on the same machine, three different machine fingerprints will be generated for the same machine (would be treated as three different machines). If user has installed different versions of the same OS, they are all treated same. No matter which Windows OS user has installed on a machine, same fingerprint will be generated for all. Same holds true for Linux and Mac OS X. Machine fingerprint cannot be used to determine any information about the hardware.
Verified trial also uses online activation. It uses the single trial key to activate your product. It ensures that trial doesn't reset even if user formats the machine as the hardware on which the trial key is used gets registered for the key.
As the count of trial activations is usually much higher than product activations, TEN trial activations consume ONE activation from your plan. When a trial user activates using a product key, trial activation registered against the user's machine is automatically freed up, hence allowing more trial activations.