The filter feature allows you to choose from a pre-saved list of views or gives you the option to create your own.
A view will group and order Records as well as filter down Records based on values for fields. One example would be a list of Projects filtered down to show the projects that are status red, grouped by business unit and ordered by project title.
Your system administrator will set a default view for the App which you will see the first time you access a Report. You will then have the option to change the view and this will remain as the view you see for the Report each time you access it until changed again.
Commonly used filters can be stored for use again in the future. They can be saved as personal filters for use only by the user who created it, team filters if you would like to make the filter available to members of your team or a global filter if it is beneficial to all users of the App.