Views lists stuff. Views works best listing simple stuff. You want values in nodes. The Drupal 7 Field system helps you easily add extra stuff and that makes Views easier.
There are three modules in the Field group,
Field SQL storage, and
Field UI. The Field module and the Field SQL storage module are in core and required for everything. The Field UI module is in core and is optional. You only use Field UI when you add your own fields.
You can easily add stuff to Drupal using modules and on some occasions you will want to add stuff that is not added by modules. If you have some PHP coding experience, you can easily add stuff through your own add-on modules and not everyone has PHP coding experience. Field UI fills the gap. The user interface for Field UI is similar to Views. If you like Views and understand Views, Field UI is for you.
The important part of Field is the ability to add data that is easily accessed in Views. Anything added through Field UI is automatically available for selection and sorting in Views. You have to investigate and practice with Fields UI to give you the maximum opportunity to build data structures easily listed by Views.
When you need to alter the fields, you can sometimes make significant changes using mixtures of Actions, Rules, and Triggers, all without adding on a module or writing PHP code.