Semiconductors can change their electrical properties, degree of conduction, by the addition of impurities. This is the reason why silicon needs to be in such a pure form (approx. 99.99% pure). The procedure in which you add impurities to a semiconductor is called doping. The impurities that are used are called dopants. There are two different types of dopants. They are called n-type and p-type dopants.

N-type doping
Some of the most common n-type dopants are located in the group 15 of the periodic table. One example of such dopant is the element phosphorus (P). The n-type dopant introduces negatively charged electrons to the semiconductor. Sometimes these dopants are called donators because they donate electrons to the semiconductor

P-type doping
The other type of dopants, the p-types, can be found in the group 13 of the periodic table. The element boron (B) is one example of such a p-type dopant. These p-type dopants introduce something-called holes in the semiconductor, which is nothing but taking electrons from the semicondutor. Because of these electron deficiencies, the total negative charge is reduced and the holes (positive charges) are left behind.