Usually, with programming languages, that refers to having a wide standard library that allows you to complete many basic or common functions without downloading 3rd party or additional libraries.
Yeah, that's what Python's "batteries included" slogan means. Perl and Python not only ship with lots of libraries, but have built-in functions for file manipulation and running arbitrary shell commands as part of the core language: https://news.ycombinator.com/item?id=42509544
