A mapped field looks up the existing field's value and determines what new value to use for itself.
In the example above, if the person's Group contains the text "Adults", the new field Check in point will have the value "Parking lot". If it contains "College students", the new field's value will be "Front lobby". You can have any number of mappings here, each defining the source value and a result value.
The mechanisms for mapping here will vary depending on the type of the source field: a numeric source field will have minimum/maximum numbers, a date source field will have minimum/maximum dates. Result types will vary as well, providing a way of entering the appropriate types of result values.