I find Drupal 8 module management to be confusing, but one thing I’ve learned is that you can install and remove Drupal 8 modules with Composer at the command line.
Adding a Drupal 8 module with Composer
The short story is that to add a new module — such as the reCAPTCHA anti-spam module — you type this command at the command line (in the root directory of your Drupal 8 website) to install it:
The process of updating a Drupal 8 website changed dramatically back in March-April, 2018, so I deleted the older content on this page and replaced it with the content below.
As of April, 2018 you now need to use Composer along with Drush to update your website. Here are my very brief notes on how to do this: