This document provides an overview of key concepts in semiconductor physics. It begins by introducing the crystal structure of silicon and how dopants can create an excess or deficiency of electrons (N-type or P-type silicon). It then discusses the energy band model and defines important terms like the band gap, Fermi energy level, density of states, and thermal equilibrium. The document derives expressions for the concentrations of electrons and holes as a function of doping, temperature, and the Fermi level position. It also examines intrinsic carrier concentration and how doping affects charge neutrality. Overall, the document establishes fundamental principles for understanding how electrons and holes behave in semiconductors.