The external view is the view of the data used by customers or people who input and view data, a conceptual view is useful for the database designer and the internal view is used for the detailed programming of the database.
A customer does not need to see as much information as the administrator or programmer of the database.
The external view is the view that the customer would see. If you made an app which used a database to collect data, you might want to give users a simple form to add new information to the app. For example, if there was an app which people used for bird watching it could simply have a form which includes:
The app user does not need to see the whole database to add their information. It is possible for a database user to work with a database and never actually see the tables that are used to store the data.
This view shows how the tables are all connected. It could be used to plan changes to the database. This view can also be presented using SQL.
This is the view that shows the detail of how the computer sees the database. It might include details of how files are structured and stored and include hex or binary references to bytes of data. It is complex and would only be used by the database programmer.