Question

what is the difference between python 2.x and python 3.x?

Answer 1

Python 3.x is new and with a different code syntax (it doesn't matter much for beginners but it causes subtle problems for advanced usage). So is it recommended to learn python 3.x. There are some minor changes as well

Answer 2

There are differences, but they are not much, you can get a list of the differences here:
http://nbviewer.ipython.org/github/rasbt/python_reference/blob/master/tutorials/key_differences_between_python_2_and_3.ipynb or find more in the attached file.