1. Go to Analysis > Information Library.  Click Add an ad-hoc query.  
  2. Select the source view of Constituent query and click Ok.
  3. To see any constituent records that were changed by that user, In the middle column, under System Fields, click Changed by Username and move to Include Records Where.  Set the criteria to Equal to, then choose the username from the dropdown and click Ok.
  4. In the middle column, under System Fields, click Date Changed and move to Include Records Where.  Set the time period you're looking for updates made by this user, such as today, and click OK.
  5. To see specific parts of the record that were changed, such as to see addresses that were changed by that user, select Addresses on the left, and in the middle column, under System Fields, click Changed by Username and move to Include Records Where and set the criteria to Equal, select that username from the dropdown and click OK.
  6. In Results Fields to Display, move the information you want to see, such as Changed by Username, Date Changed, Added by Username, Date added
  7. Go to the Set Save Options tab, name the query, and click Save and Close.

To see more details about exactly what was changed on the constituent record, you can run the History report on a constituent record.

While previewing the results of the query,
  1. Click on the constituent result, then click Browse.
  2. Choose page definition Constituent History Page, click Ok.
  3. Select to show the date range you're interested in, filter on the user you're interested in, then click View Report.