The Functions integration allows for scripts to be discoverable through autocomplete while authoring scripts. Functions can be "disabled" by disabling the containing module.
  1. 1.
    Begin by adding a script library called "Functions" to a module. This can be created by the new module wizard.
  2. 2.
    Add a script to the "Functions" script library with a name that represents the purpose.
  3. 3.
    Use the command Import-Function to discover the available functions.
Module Creation
Note: It's best practice to create function scripts that follow the Verb-Noun pattern as outlined by Microsoft.
Shared Functions Library
Autocomplete in ISE
Here's a short video on authoring custom functions.
Creating Functions