By Maff 14/09/2018
Features is a method of synchronising Drupal site settings and structure (eg, content types, views, etc) between different instances, such as the live site, dev site and your local copies.
By generating a feature, you select a portion of the site's settings that exist in the database and copy them to code. This is similar to if you were to programatically generate a content type and put it into a module. The features module will take an existing content type generated through the front-end GUI and replicate it using code. This is also similar to what would happen if you choose "export" from views, as well as many other modules that have similar functionality to this. However, this doesn't apply to generated content such as nodes, users, taxonomy terms, menu links, etc. Certain contrib modules can allow you to do this, for example if your content has a UUID (which means it can be versioned), but it tends to be an anti-pattern. Normally this stuff would be generated manual