What are "hyperthreading" and "virtual cores"?

Question

I'm new in this computer terms. So anyone can explain to me what "virtual cores" and "hyperthreading" are at greatest detail a layman can understand?

People told me that virtual cores are imaginary cores acting like a physical core. If that is so, then can I make my AMD v105 processor single core a dual core processor?

Is it also possible to hyperthread my CPU? Are these functions built in?

Solution

Hyperthreading is a hardware feature and is not portable to other CPUs. Hyperthreading is essentially a duplication of the architectural and state hardware that surrounds the actual central processing units on a processor core.

It makes a single core processor look like a dual-core processor so that the data processing parts of the processor can be used slightly more efficiently. It is not as good as having another full processor performance-wise, but it does make slightly better use of the processor when under heavy use.

See this picture for a vague example, and if you want to read more then there's a good article on PCStats: