PyPy is faster than CPython in some tasks, primarily due to its use of JIT (Just-In-Time) compilation. While standard CPython is a pure interpreter (it executes bytecode one at a time), PyPy analyzes the code as it runs. It identifies "hot" sections (such as loops that execute thousands of times) and compiles them into fast machine code on the fly.

This question is very rare.

Basically, you'll hear it in two scenarios:

1. The person asking this question is a buzzkill who wants to assert themselves at the expense of those who don't know their stuff or who wants to find like-minded buzzkills.
2. The company you're interviewing for actually uses PyPy, and they need someone who understands how it works to write efficient and fast programs.

As you can imagine, the first scenario is much more common than the second.