Wondering what separates people who catch concepts quickly v/s who don't

I had a friend in college who used to read proofs/math and later was able to answer the same in exams whereas me on the other hand, I need to do it on my own and still make so many silly mistakes. I sometimes forget the concept I studied the day before if I didn't practise it enough. It also happens that I have been studying the subject since a long time and still not able to perform that well in the exam .

What separates me and her ? Is it just focus or she is just some genius ?