Sender Framework Policy (SPF) is a tool to you can use to advertise what sources are legitimately allowed to originate email for your domain names. It is useful for distancing yourself from forged email with your domain and can help protect recipients of real email from you (such as your customers and members) from some forms of phishing attacks.
It works by publishing a "blob" of data about your domain over DNS, this wizard is to help you create that blob.