What it does: the component enhances the standard search with checkboxes, indicating which mambots you want to use per search. E.g. if you have search mambots for your forum, your content and your news items, you can pick which one you want to search each time. By default, Joomla searches all published mambots and combines the results. With Advanced Search, you can choose.
Using their module you can display a search box to search a particular part of your site (providing you have a search mambot for that).
Currently, this is all the component does. Some more features are in the pipe line. E.g. include or exclude particular sections or categories. A personal favorite for me would be an extra sorting option, allowing it to sort by keyword density.
If you need it, shell out the 10 bucks to download it. Don't expect too much, but the basic functionality is solid.