When you enter the IP.Tree window, you will see a Tree representing the IPs in your network, like this:

The IP.Tree main window.
Each [+] symbol represents a "node" that can be expanded by clicking on it, or selecting the record and pressing the + key. At first sight, you will see all your networks, one below the other, as shown above in the window sample.
The IP.Tree has three levels, the "root" one is the "networks" level, following by the "ranges" level, and the latest is the "devices" level.
When you expand a node, you reveal what's in the following level, as shown below:

IP.Tree window expanding one branch.
When there is an overlap on a Range, you will see a "(* range conflict *)" message.
When two or more IPs are repeated, you will see an "(* IP Conflict *)" message.
In the following topics you will see what are the buttons for.