When opening a query and the following tabs are observed, the query is the resulting output query of a completed Query Merge.
Tabs in Merged Query

The criteria for this query are contained in the two queries used to create the merge. That information can be found in Query Options under Tools in the opened query.

The Description field on the General tab defaults to listing the two queries used and the operator:
Query Options General tab

And the Query Merge details are on the Record Processing tab, where you can edit the queries used or change the operator to update/redo this merge:
Query Options Record Processing tab

You can also query or filter further within the results of the merged query by setting the merged query in a new query:
  1. In the desired merged query, note the name of the Query and the Query type from Tools > Query Options > General tab. Close this query.
  2. Start a new dynamic query of the same type noted in step #1.
  3. In the new query, go to Tools > Query Options > Record Processing tab.
  4. Mark Select from query.
  5. Click the binoculars and search for query name noted in step #1.
  6. Double click on the query to add to the field.
  7. Click OK.
  8. Click on the Criteria tab to add the desired filters. This query will only search among the results of the merged query.