I came across this statement in the book "Quantum Field theory and the Standard Model".

"We would now like to find all the representations of the Lorentz group.
The Lorentz group itself is a mathematical object independent of any particular representation. To extract the group away from its representations, it is easiest to look
at infinitesimal transformations."

I didn't understand how the concept of representation is related to infinitesimal transformation? How are these two concepts related? And what new insight in Physics it gives us?