Original: The name hemoglobin is derived from the words heme and globin, reflecting the fact that each subunit of hemoglobin is a globular protein with an embedded heme (or haem) group. Each heme group contains one iron atom, that can bind one oxygen molecule through ion-induced dipole forces.
Simplified: Hemoglobin is made from three parts: a heme molecule, a globin chain, and an iron atom.