What is a dongle and why it emulate?

The dongle is part of the software protection in the form of a LPT or USB key.
It works on a simple principle, dongle plugged into a computer – protected program works, dongle unplugged – protected program does not work.
In any case, if you are an authorized user of the program protected by dongle, to protect themselves from the loss of the dongle or breakage – beter make ordering emulator.