Hermeticism is an ancient occultic philosophy which originated during cultural exchange during Greece and Egypt. It is said to have been started by the mythohistorial figure 
Hermes Trismegistus, who is claimed to be deified as Thoth and Hermes by the Egyptians and Greeks respectively. It is unknown which country Hermes Trismegistus was born in, what is known is that he started his teachings in Egypt, and that many used to travel there to learn from him.
History
Beliefs
Hermeticism as a philosophy begins with several presuppositions and axioms. The Axioms are the principles of Hermeticism. They will be listed (with simplified explainations) here.
- The Principle of Mentalism
- The Principle of Correspondence
- The Principle of Vibration
- The Principle of Polarity
- The Principle of Rhythm
- The Principle of Cause and Effect
- The Principle of Gender
The Principle of Mentalism
The principle of mentalism states that everything materially apparent and manifest within the universe (and the universe itself) is mental. Part of a (single, very large) mind, a mental projection. Not unlike a dream. The masters often stress that this does not mean one can ignore reality, as despite being mental, everything is still very real.
The Principle of Correspondence
Often expressed with the older saying "As Above, So Below; As Below, So Above." The Principle of Correspondence offers the understanding that the laws and phenomena of lower planes have corresponding laws and phenomena on the higher planes, and vice versa.
The Principle of Vibration
"Nothing rests, everything moves, everything vibrates." - The Kybalion The Principle of Vibrations states the simple truth that nothing is ever at rest. Everything has vibration and movement along some dimension or plane of energy. The variations in these vibrations are what give everything on all planes their different properties.
The Principle of Polarity
The Principle of Polarity states that all phenomenon are manifestations of properties which have two sides. e.g poles. Every true property of things follows this rules. Hot and Cold are poles of temperature. Love and Hatred are the poles of emotional affinity. A void and a filled space are the poles of Substance (and its presence). If you take a truly polar property, and move slowly from one pole to the other, you will notice no exact line where something demonstrating one pole, suddenly and in binary fashion switches to manifesting its opposite aspect. As the saying goes, "Every falsehood is half true, every truth is half false."