This file contains the following topics: The main field, the internal field, the external field, the magnetic induction due to a magnetic dipole, magnetic potential due to more complex configurations, power spectrum of the magnetic field, downward continuation, secular variation, source of the internal field: the geodynamo, crustal field and rock magnetism, magnetization, other types of magnetization, magnetic cleaning procedures, paleomagnetism, field reversals, qualitative arguments that explain the need for core-mantle coupling, reversals: time scale, sea floor spreading, magnetic anomalies, magnetic anomaly profiles.