When you send out a mailing, invitation to an event, etc. you'll usually create a Contact in a constituent's journal showing that they were sent that communication. Down the road, you may want to create a query to find all constituents that were sent that particular communication. You can do this by creating a query using the Contact Subject Text field as criteria.
You can create a query to find all constituents with a certain contact by following these steps:
1. Click Queries 2. Select a category to store this query in (Ex: Base) 3. Click New Query 4. Name the query 5. Select Base for Query Category 6. Select All Constituents for Query 7. Select Journal Entries for Data Return Type 8. Select Match each Criteria for Criteria Matching 9. Under Browse Fields select Journal from the drop down box 10. Click Contact Subject Text 11. Type in the subject of the contact you are looking for 12. Click Save and Preview