So i actually have many words that i know of, and are familiar with such as : The Hamiltonian Operator The Hermitian Operator The Lagrangian Eigen Values/States However, i am struggling with how these things work, and when to apply them, and what they actually mean. Many of the physics lectures i watch tend to glaze over them. For simplicity sake, lets just start with the Lagrangian. What exactly is it? When is it applied, and can someone offer an example of its use?