There are many questions dealing with pyglet and pygame, but what I want to know is difference in theses two, in simple terms.
Not in technical terms, not experimental features and all that.
They are both libraries, both API, both for creation of games and multimedia apps, right?
Just in plain English, for someone like me, relative begginer, who has finished course about Python in Codecademy and read Head first Python book.
PyGame is low-level library. You have to do all on your own - starting at mainloop and all functions called by mainloop. You can do it in different ways. 
(And you can learn something about mainloops in Pyglet, Tkinter, PyQt, wxPython and other GUIs, not only in Python)
Pyglet is framework - it has already mainloop and you can't change it and you can't see how it works. You override functions which mainloop calls. You have to keep its rules.
Difference between pyglet and pygame, in simple words?