Other modules can provide a user interface for managing custom fields via a web browser as well as a wide and flexible variety of data type, form element, and display format capabilities.
The administrator (again, via a UI) creates two Field Instances, one attaching the field ‘subtitle’ to the ‘node’ bundle ‘article’ and one attaching the field ‘photo’ to the ‘node’ bundle ‘article’.
When the node system uses the Field Attach API to load all fields for an Article node, it passes the node’s entity type (which is ‘node’) and content type (which is ‘article’) as the node’s bundle.
Using the Views module, you can fetch content from the database of your site and present it to the user as lists, posts, galleries, tables, maps, graphs, menu items, blocks, reports, forum posts etc.