What is the $base in code sample?

When setting up WordPress for MultiSite, the EE tutorials mention a:

$base = '/';

…in their code sample (Example: https://easyengine.io/wordpress-nginx/tutorials/multisite/create-a-network/). See images below:


However, I see no such code in the “Settings > Network Setup” area. See image below:

Two questions:

  1. What does $base = '/'; do?

  2. Why is it in the code from EE, but not in the code recommended by WordPress itself?

Whatever the:

$base = '/';

…code is supposed to be doing, removing it doesn’t seem to effect WordPress functionality.