The user can create single Filters and Value Fields using the Meta data field or Table and column tabs in the Add view. It is also possible to create a filter group. However, a search can be extremely more flexible: filters in value fields, bind fields, groups within groups, and many other possibilities. For now, disregard these extraordinary features, because they will normally not be needed and are not documented.
The Predefined tab in the Add view enables creation of elements, which the UI does not necessarily support editing or displaying of. In other words, be wary of using predefined elements because they might be overly complex and offer a lot less transparency.