What is matplotlib backends and how it is implemented? How does it simplify the use of wxpython when I use matplotlib wxAgg backend?
For a description of what matplotlib is, see http://matplotlib.sourceforge.net/. I would download the source to see how it's implemented.
I don't think it really simplifies the user of wxPython though. You use matplotlib for graphing and similar activities. You can use wxPython to display the graphs. There are examples on the matplotlib website and in the wxPython wiki.