The Quick Filter Bar lies beneath the Column Header, providing a shortcut to creating Column Filters manually in the filter dropdown - the 2 components always stay in sync.
The left of the Quick Filter Bar provides a dropdown showing all the 'Predicates' available for that Column, including any Custom Predicates that have been created.
Any Predicate that requires an input (e.g. 'GreaterThan') will show a textbox to enable text entry; those that do not (e.g. 'Postive') will show it as disabled.
If the 'IN' predicate is selected then a list will appear showing all distinct values in the column to enable a selection to be made.
You can change also select frequently used Predicates by typing a 'wild card' in the Quick Filter Bar, e.g. >, <,=, != and IN (for lists) - press 'Escape' to clear the Predicate.
The default Predicate for Numeric and Date columns is 'Equals' and for String columns is 'Between' - however this can be changed in Search Options.