They are called ball-joint-dolls or BJD for short. Most come from Korea, although some of the cheaper ones are now made in China (isn't everything?) and Japan also makes the brand Volks. There are many, many different companies out there. They come in different sizes from very tiny to about 70cm tall. They are made of resin and they are expensive. You can probably find secondary market dolls on Ebay. Very addictive!
Depending on the company that makes them, you can get several options in sculpts from realistic (my preference) to fantasy (elves, vampires, etc.), different skin tones.
Have fun in your search!