There are four settings for field mode;

• Copy – Used to copy a value from the source data into the relevant location in OpenGround. This is the setting most commonly used.
  
• Evaluate – Used to run a query on the incoming data and return a result based on the output of this query. This can be used to do a variety of things. More information can be found in the Expressions section.
  
• Constant – A constant will put a fixed value into the field for every newly created row
  
• Ignore - An Ignore mapping suppresses Warnings about unmapped fields. Also, you will typically get "false Warnings" about unmapped fields if a field is imported via an 'Evaluate' expression, in which case you can use an Ignore mapping to suppress that false Warning.