Features is a module which generates modules for us. You can then extend that module just as you would any other Drupal module. In this video we'll add some additional code to our feature to make it more complete for our needs, outside of the realm of what Features itself can provide.
The features module (and the drush command) are pretty smart about not overwriting custom changes, and your chances of overwriting your custom code are pretty slim. When features exports a module it creates a .module file with only one line of code in it. Which is an include for another file: mymodule.features.inc. Features then puts all of the automatically generated code into this included file. When you regenerate or update a feature it just uses the existing mymodule.module file which maintains any code that you wrote, and then regenerates the mymodule.features.inc and associated files.