The difference between the Exact Search and Broad Search, is that the Exact search only searches ebay listings for those listing that contain the specific model number of the tool battery or charger for this page(It searches for a single model number only), whereas the Broad Search also searches for all the model numbers that are compatible with the tool, battery or charger listed on this page.
So, if this page is for a battery, the exact search will search only for that model number. Now it may show non-batteries, as it is only looking for the model number. A broad search will, however, search for the battery model number, the charger model number, the drill model number, etc... The broad search will result in more results, but is not as likely to include the exact item listed on this page.
Hope that helps, explain the difference. Sometimes both results will be the same as well, if all listings contain the page model number.