This is to verify your identity. Valid ID scan means copy of passport or government issues identification card. This is optional and based on you own discretion. Some hosts (and guests) may require verified identity before accepting the booking. Scan should be in PNG or JPG format.
For verification purpose you will need also upload a clear photo where your face is recognisable to your profile image (in Upload Image section above). Your ID scan will not be shown to any other users than admin.
Admin will get notified about your ID scan upload and will compare the two images to verify your identity. Once verified, your profile will have a verified tag.