First of all, when you download Python to your system, you are specifically downloading a Python interpreter. As the term suggests, it is a program that can take in Python code, interpret it, and translate that code into lower-level machine language, thus executing the Python program. If you have both Python 2.7 and Python 3.6 on your computer, for example, this means that you have two different and separate Python interpreters—in essence, you have two ways to interpret a specific Python program.