Fields are used to show up data on the web page and gather input from users. To add a new field from the Web pages editor, unfold the Components → ADD NEW FIELD and drag and drop it into the Working area.
A Field is related to a data type, not a web page. So, if you remove a field from a web page view, the field still exists. You can see such fields in the EXISTING FIELDS section on the Components panel. Moreover, all the fields are listed on the data type details page, namely Fields section.
Data binding is enabled out of the box. In other words, fields changes from blocks are immediately shown in corresponding UI control. And vice versa, user input is available in blocks for reading. This data binding is extensively illustrated on the Toggle a job example.