I have taken a course on group theory a few years ago. I have also used a little bit of group theory in a particle physics course.
However, now I have started with AdS/CFT and string theory and I am always confused when references to group theory are made.
Here is one of many examples: Say I study $\operatorname{AdS}_5 \times S^5$. Then someone mention that the isometry group of this is $\operatorname{SO}(4,2) \times \operatorname{SO}(6)$.
I could never have guessed the underlying isometry group, and I know so little group theory I don't even know why I need it...
In papers, authors typically mention the underlying group of the theory, but never does anything explicitly with that information (to my knowledge) which has allowed me to be ignorant about this for so long.
What resources are good to be able to obtain/understand the underlying group and what it does for the theory?
I know the question is very general but any guidance is very much appreciated.