I have started working on differential geometry very recently. I am little bit familiar with mathematical concepts such as manifolds, differential forms and associated concepts. As I was speeding through I caught interest in Lie groups and whose invaluable connection with the symmetries. I would be happy if anybody answers to these few questions.
I want to know what is a symmetry from the mathematical point of view?
How are $su2$, $su3$, and other symmetries first formulated?
What was the motivation?
How do we identify internal symmetries and corresponding conserved physical quantities?