Getting Started with Forms in Drupal 8
Forms are an essential part of any web application. They are the primary mechanism for collecting input from our users, and without them Drupal wouldn't be very useful. As such, they're also one of the first things people want to learn when they start learning Drupal. Forms are fundamental to creating Drupal modules, whether you're asking someone to leave a review of your video or giving an administrator the option to turn JavaScript aggregation off.