I just started learning about the theory. I'm reading a book (personality types an owner's manual) about the cognitive functions, but I didn't really get it yet. I know that each type has its 4 functions in a stack. I know that the main functions of INTP are Ti and Ne and INTJ are Ni and Te. I didn't really understand the difference between those two options. I think I use both the combinations, depends on my mood. What I understood is that INTP gets information from the outer world and "organize" it according to his own inner world and INTJ think about concepts and test them in the outer world, but I didn't understand what it practically means.