Stem cells are the body's "master" cells that regenerate the body's many cells, tissues, and organs. Most cells in your body can only make new cells of the same type – blood cells make blood cells, skin cells make more skins cells and so on.
Stem cells are unique not only because they can turn into many different types of cells – a stem cell might create blood, kidney, heart, or bone for example – but also because they can divide many more times than other cells.
There are two broad types of stem cells: embryonic stem cells and adult stem cells. 
While there has been much debate on the ethical issues surrounding the use of embryonic stem cells, adult stem cells are free of this controversy and only adult stem cells, to date, have been used to treat people.
Dental stem cells are one type of adult stem cells and are very similar to the adult stem cells that have been used to treat people for a variety of conditions.