Creating a draft can be useful so you can email the tenant(s) (and guarantor if one) a copy of the agreement in the early stages before ready for signing.
The field "is this to be a draft?" is near the top when creating or editing a tenancy, just below insert profile.
If this field is set to "yes", dates you enter will be replaced with the words "This is a DRAFT - for information only".
This is useful to set "yes" if you want to email the agreement to the prospective tenants before all parties are ready for signing. Because it contains the words "this is a draft", it's clear that's all the agreement is at this stage - a draft.
If you intend to send the agreement for signing straight away you can leave this as no.
When you are ready for final signing, you can edit the agreement later and set this back to "no" and any dates inserted will be whatever you entered (or blank).