Classic and Evolution are two different types of firmware grade/network.
Evolution provides more features and functionality than Classic, and new features will be only be introduced for Evolution.
Only devices of the same firmware grade can be used in the same type of network (i.e. Classic devices operate on Classic networks; Evolution devices operate on Evolution networks).
The original processor used in some older Casambi devices restricted the introduction of new features and functionality. First the hardware processor was upgraded and then the Evolution firmware grade was developed to take advantage of this. This means that some Classic configured hardware is already equipped with the latest processor.
Casambi devices have Classic or Evolution firmware pre-configured. Depending on the processor the device uses, it may or may not be possible to change the firmware grade (i.e. Classic to Evolution, or Evolution to Classic).