What is Group Theory?

Helloooo, Im a high school student that is currently learning about logarithims,exponential functions and graphing, and in the course my professor started off by saying that he has a Nanotechnology Masters Degree, this got me curious as to what has he seen in math? So I asked him what is the hardest subject he had to learn during his student years, he told me it was Group Theory and just by hearing the word theory I could assume it was a hard topic/subject.

So now I ask, what exactly makes Group Theory so hard to learn and understand or what are your thoughts on it? Of course im only still a mere high school student that has much learning ahead, but I want to know what thoughts everyone has about this topic which is technically my teachers "Nightmare".

Just curious, best of luck to anyone studying for a degree!

Author: Therealgodzilla87