Let's say you want to find everyone in California, but you might be storing both California and CA in your Database. To include all applicable people, you could use two State filters, but it's easier with one.
1. Go to Marketing Activities.
2. Find and select a smart list and click the Smart List tab.
3. Click the plus sign on the filter.
4. You can choose values from the left or just type them on the right then click OK.