The Earth has a magnetic field generated by circulating ions in its liquid iron core. The field emerges from the geographic North Pole and re-enters at the South Pole, and its strength varies by location. The magnetic declination is the angle between magnetic and geographic axes, while magnetic inclination is the angle the field makes with the horizontal. Materials can be classified as diamagnetic, paramagnetic, or ferromagnetic based on how their atoms respond to magnetic fields. Ferromagnetic materials like iron contain magnetic domains that align when magnetized. The hysteresis curve shows the relationship between magnetic field strength and flux density, exhibiting properties like retentivity and coercivity that differ between soft iron and steel.