Python 2 is an old version of the language that is incompatible with the 3.x line of releases. The language is mostly the same, but many details, especially how built-in objects like dictionaries and strings work, have changed considerably, and a lot of deprecated features have finally been removed in the 3.x line. Note that Python 2 is not supported upstream after 2020-01-01, please use the python3 package instead if you can. This package also provides the 'python2' executable.