# Information contained in Lagrangians and actions [duplicate]

I've been looking into analytical mechanics with the intention of finding out more about Lagrangians and actions. As far as I currently understand it, the Lagrangian is formed with positions and velocities and then operated on using the Euler-Lagrange equation to determine the laws of motion. However, talking to more experienced physicists than myself, they always say that there's more than just equations of motion in a Lagrangian. Also, when I look at Lagrangians defined for fields, I cannot interpret them (probably because I'm coming at it from a mechanical point of view). I guess that's two questions in one, but the overriding question I have is what information can be obtained from a Lagrangian, and taking it beyond mechanical systems what does it generally represent? Links to websites and book recommendations would be greatly appreciated.

## marked as duplicate by ACuriousMind♦, Kyle Kanos, Qmechanic♦Apr 16 '15 at 13:00

What, in a first reading says is this: When a dynamical system moves from a position 1 at time t1 to a position 2 at t2 with generalized coordinates q the path the system will follow is that where the $$\int {L(q,q',t)dt}$$ from 1 to 2 takes the least value, that is the statical value $$δ \int{Ldt}=0$$