When listing tools for the current document in the Tool Library, the tool list also includes all the operations by default. This lets you easily see which operations are using a particular tool and the different feeds and speeds for each operation (assuming feed and speed columns are visible).
On documents with many operations, you have the option to hide the operations by unchecking the Show Operations checkbox.
Tool Library with Show Operations enabled, showing both tools and operations in the tool list
With this option disabled, the operations are no longer shown and you get a clearer view of the tools in the document.
Tool Library with Show Operations disabled, showing only the tools
Regardless of whether operations are shown or not, the tools that are in use in any operation are displayed in bold. Tools highlighted in orange indicate that the tools have conflicting tool numbers, which may potentially be a problem when posting to the CNC control/machine.