What does bukkit permissions.yml do?

I need to add a permission to all users for one of my plugins in Spigot server version 1.14.3: Citizens 2. Since I use no permission plugin, I edit permissions.yml in the root directory of the server to the following:

Code:

groups:
  Players:
    default: true
    permissions:
    - citizens.npc.talk
    inheritance: []
    info:
      prefix: '&7[Player] '
      build: false
      suffix: ''

However, it didn't work, so I learned elsewhere that apparently "permissions.yml does nothing on its own...The permissions.yml file is used only to create custom permissions node aliases and group nodes."

My question is what does that file even do then. What does "creating custom permissions node alias and group nodes" mean?