At the far right of the toolbar immediately above your grid, you'll find a drop-down list of your rules/rulesets. Rulesets appear in-between square brackets.
Your list is now color-coded according to the selected rule or ruleset.
Look at the bottom right corner of the grid. yilter buttons have been added. One button per rule (in this case the ruleset had 2 rules).
Each button tells you how many record meet the rule criteria. If you click the button, only the records meeting the criteria will appear in the list.
NOTE: Filtering your list view by clicking on a filter button does not affect your lookup. It only hides the records not included in the filter. If you click again, the hidden records will reappear. The circle next to the filter is either hollow (filter not applied) or full (filter applied).
Note how the circle at the right of both filters is hollow. No filter is applied.
The circle next to the first filter is full. The filter is applied.