The Search list window contains the latest generated search list.
A search list is a list of search matches generated from the Search and Replace dialog.
Once a search list is generated, this window will look like this:
You can see how this list contains all the matches of the performed search. Each file is displayed on a foldable tree-like structure and clicking on any of the matches will bring the corresponding document into view.
To generate a match list, you should use the search and replace dialog.