A key ingredient in making electronic components are semiconductors. A semiconductor is typically made of silicon or germanium, as they both have tightly-packed structures that allow a current to flow through them. This happens in one of two ways.
A n-type semiconductor is one through which charge is carried, negatively, by an excess of electrons in the substance. If you add an extra charge to one end of a system, the charge next to it necessarily moves over towards the next charge, which moves as well. In this way, a negative charge can be transferred.
P-type semiconductors are the opposite. Charge in this case moves to where there is a shortage of charges, or a "hole". As a charge moves to fill this "hole", the position it formerly occupied becomes a new "hole", which is then filled by the following charge. In this way, the hole itself moves (in the opposite direction to that of the charges).
Semiconductors, or more importantly their combination, are important in the creation of many electronic components, as these materials often determine where and how charge can or cannot flow (to produce a current).