Python - interpreted vs compiled

[codecraig]

Hi,
  I have a question about Python.  I know that it is an interpreted
language, meaning a python program is converted to binary on the fly
each time it is run, or compiled.
  What would be the purpose of compiling?  I guess the compiled python
code (question, is compiled python code called byte code?..if not, what
is it called?) is not readable since it is not plain text, which may be
a reason for compiling...but why else??

Thanks.