Where is Python language used?
Many websites uses Django or Zope/Plone web framework, these are written in Python.
Python is used a lot for writing system administration software, usually when bash scripts (shell script) isn't up to the job, but going C/C++ is an overkill. This is also the spectrum where perl, awk, etc stands. Gentoo's emerge/portage is one example. Mercurial/HG is a distributed version control system (DVCS) written in python.
Many desktop applications are also written in Python. The original Bittorrent was written in python.
Python is also used as the scripting languages for GIMP, Inkscape, Blender, OpenOffice, etc. Python allows advanced users to write plugins and access advanced functionalities that cannot typically be used through a GUI.
I am a web developer and usually use PHP, JavaScript or MySQL.
I have heard lot about Python. But I have no idea where it is used and why it is used.
Just like  PHP, ASP, ColdFusion, .NET are used to build websites, and 
C, C++, Java are used to build software or desktop apps.
Where does Python fit in this?
What can Python do that these other languages cannot do?