Lagrangian mechanics[0] is a compact way to describe the dynamics of a physical system using a single object/equation. You can think of it a a generic description of a system, from which you can extract the equations of motions of the particles forming that system: which is generally an important part of what physicists wants to achieve, i.e. predicting the motion of objects.
I'm not qualified to provide you with a more precise, still concise and (hopefully) still accurate description. However, if you want to dig further, the most beginner friendly introduction that I've stumbled upon is Susskind's The Theoretical Minimum - Classical Mechanics [1](there's a book & a series of videos).
I'm not qualified to provide you with a more precise, still concise and (hopefully) still accurate description. However, if you want to dig further, the most beginner friendly introduction that I've stumbled upon is Susskind's The Theoretical Minimum - Classical Mechanics [1](there's a book & a series of videos).
[0]: https://en.wikipedia.org/wiki/Lagrangian_mechanics
[1]: https://en.wikipedia.org/wiki/The_Theoretical_Minimum