In March 1916, the physicist Albert Einstein published his most famous work: the General Theory of Relativity [1]. Einstein presented his theory on 25 November 1915 at the Prussian Academy of Sciences; however, the document was published only in 1916 in Annalen der Physik journal. It was after the publication that this theory had worldwide repercussions. This study focuses on some details of Einstein's life and his two scientific theories: relativity (or Special) and General Relativity. The first was published in 1905, completing previous studies of the Dutch physicist Hendrik Lorentz, while the second is the generalization of Newton's gravitation theory. It takes into account the findings ideas on relativity of space and time and proposes a generalization of the principle of relativity of motion for systems that include gravitational fields.