A pure semiconductor is intrinsic. Thermal excitation creates electron-hole pairs, so electrons in the conduction band and holes in the valence band both contribute to current.

Adding a small concentration of suitable impurity atoms is doping.

A donor contributes an electron that can enter conducting states easily, producing n-type material in which electrons are the majority carriers.

An acceptor creates an easily occupied missing-electron state, producing p-type material in which holes are the majority carriers.

Doping does not make the material macroscopically charged: ionized dopant atoms are balanced by the mobile carriers they create. It changes which carrier type is abundant and therefore changes conductivity and junction behavior.

Semiconductor devices are built by arranging regions with different doping so carrier motion can be controlled by electric fields and applied voltages.