The USB-eLicenser is also required to run Steinberg VST instruments, but is not included in the product boxes and must be purchased separately if no USB-eLicenser/Steinberg Key is already present on the system. The USB-eLicenser is actually a tiny computer which stores licenses for Steinberg products, and is connected to a USB port on your computer. 

All current Steinberg products that use a copy protection device use exactly the same system. The Steinberg copy protection system allows the storage of several licenses on the same USB-eLicenser. Licenses can also be transferred between USB-eLicensers with certain limitations. This can be very useful, for example in the unlikely event of a Steinberg customer wishing to sell a product.