What is the difference between PyPy and Python? are there lot of differences?

[ArrC]

Hey guys,i am a python newbie,
i just read a qustion on quora where it said that quora quys used pypy (and pylon) to develop quora.

So, i want to know what are the core diff btw PyPy and Python ?

And they also talked about the lack of type check in python.

So, how does it help (strongly typed) in debugging?

Thanks