'Wrap your mind around' and 'wrap your brain around' are the same thing. It means to comprehend something, to understand it. It's usually about complex ideas that you aren't familiar with, a science or a philosophy that's new to us. It doesn't need to be that you fully understand the idea in question, just that you begin to understand what it's about.
"String Theory can be a tough thing for the average person to wrap their mind around."
"I know his ideas are radical, but give it some time to wrap your mind around them."
"This book is too difficult to read. I can't even wrap my brain around what it's trying to say."
You can switch 'mind' and 'brain' in any of the examples, or any of your own.
(not a teacher, just a language lover)
Student or Learner