This Condition located on the Contributions category tab in Search Builder is looking at the Envelope Option that is on the Member Profile and Giving tab for a person. The options are Joint, Individual, None, or not specified.
If your church uses an envelope service to mail sets of envelopes to your donors, this Condition will help you build the list to upload or email to your envelop provider.
You can find those who want to receive Joint envelopes (Mr. and Mrs. John Smith) first and then find those who want Individual envelopes (John Smith, Mary Smith). For Joint envelopes you will select Combine Couples; for Individual envelopes you will select Individual. Because this setting is on the Member Profile and on the Giving tab, it can only be edited by a user with Membership role or Finance role.
Read more about the output you will want to select when uploading a file for Mailed Envelope Sets.