The dialog also opens when you click in the Show Usages popup which lists all the occurrences of the symbol at caret.
Use this dialog to configure the search procedure and scope when looking for occurrences of the following data:
Fields, variables and parameters
Classes, tags, attributes, and references in the HTML, XML, and CSS files
Symbols at caret.
The search results are displayed in the Find tool window.
Skip results tab with one usage
Select this checkbox to be navigated directly to the found usage without the Find tool window displayed, when only one usage is found.
Open in new tab
Select this checkbox to have the results of each search shown on a separate tab of the Find tool window. If the checkbox is not selected, the search results will be shown on the current tab.