The field type dropdowns in the initialization popup have four special data types unique to Airtable: Attachment, Collaborator, Barcode, and Link to Record(s). This is for ease of use, to make it easier for you to map your Airtable columns to Bubble types. In practice, Attachment fields can be used like a list of images or files. Barcodes can be used like text. Since Collaborators and Links are native to Airtable, these fields must be pulled directly from Airtable when using a Table as data or creating/modifying records.