You created a new Cacti Tree called Customer A which you can now use to add all Customer A-specific entries. Using separate trees for customers or business units will enable you to better allow or deny access to these for specific users. You are going to see the interaction between a tree and the users later in the book.

A sub-tree item enables the creation of sub-entries to the Cacti tree. These can be entries such as "Country", "Site", or a "Business Unit". Creating sub-tree items allows end users to easily find their devices on the Cacti Tree.