The learning curve is most definitely steep, and will take place over a period of time - certainly not an hour - so your feelings are normal and just
The smarty manual gives the best examples of what the code does with outputs - though not x-cart specific - unfortunately with variables, x-cart uses hundreds if not thousands of them, and it is not possible or necessary to list the function of them all. The best way I've found to learn, is to know what you want to do, and then figure out the variables and code necessary to do it. In the process, you will gain knowledge that will help you in all areas.
Good luck.