The Ruy Lopez is, without doubt, the most ancient and most played system in the King's Opening. It is characterized by the development of the Bishop in "b5". This is a most profound move which can produce most complex and very diverse developments in the game. After 1 e4 e5 2 Nf3 Nc6 3 Bb5.
The Ruy Lopez chess opening has long been seen as white's best chance for an advantage after 1.e4 e5 2.Nf3 Nc6. Many top players and coaches believe your improvement as a chess player depends on your understanding of the Ruy Lopez chess opening.
The Ruy Lopez teaches you a lot about the classical principles of the chess opening, and the Closed Variation, with 9 h3, will deepen your understanding of chess. No matter which side of the Ruy Lopez you find yourself on, you will learn much about chess.
Of course, an opening with as much history as the Ruy Lopez will have acquired a large amount of theory. Do not let this stop you from playing one of the most respected chess openings, but take your time and enjoy every small step towards mastering the opening.