When you perform a database search, often you will be given a lot of results -more than you could ever go through. When this happens, it's important to tell the database exactly what kind of resources your looking for by applying filters.
Filters (sometimes called limiters) help take away search results you don't want. You can filter by type and date.
Type - Each of these filters helps to make sure that the kinds of results your search gives you are appropriate for research.
Date - These filters limit your results according to when they were published.