How hyperthreading processor is different from other traditional processors?

A traditional processor normally isn't 100% active. There are some parts of the processor that specialise in different processes, and they can only process one thread (or task) at a time, so when it is doing one process, other parts of the processor used for other things remain idle. A hyperthreading processor is seen in operating systems as 2 CPUs so it is given 2 threads (or tasks if you like) at once. The processor then processes one thread, and uses inactive parts of the processor to process the other thread.