...
Once you have made a simple search, you may also then edit that search in the full RT query builder, to refine the search with other attributes(Subject, owner, Queue, status etc) and or add a date range. Once you have a search query you like, you can save that search for reuse later or for inserting into a Dashboard.
...
The Simple Search Entry Screen -
For Simple Search Examples see RT 4.4 Request Tracker Simple Searches