The Labels file (optional) is an XML file that some Sawtooth Software products create when exporting data to provide additional information on the labels of variables.
Generally, you will not need to create or modify the Labels file. Even if you do need to enter additional information on variable labels, then it may still be easier to upload the variables and manually enter the additional label information directly into the project on the Settings page. It is usually more work to create a labels file by hand than it is to enter the labels directly.
The only time you might need to create the labels file by hand is when you know you are uploading from a source that is not a Sawtooth Software product, and you know it would be easier to create a file than to enter the information manually. See the Labels File Reference for more information.