FTP group
In Flow, an FTP group is where the uploaded images are temporarily stored.
Each FTP group has an associated temporary storage area where assets are placed before being uploaded to the DAM. This storage can be accessed via SAS URI, which you can use in external applications.
When creating workflows, you specify which group you want to create a workflow for. A group can contain multiple users, and every user must belong to a group.
You need to create a group before you can create users. The group is not defined by protocol or any other settings besides the upload entry point.