Redirect email means automatically forward all of your incoming email to other account that can be either in the same domain, or any other email address other than free email services such as Gmail (Why?).
In order to this:
If you decided not to login with this particular account to manage your email later, make sure you unchecked “Keep incoming email” option, so that all incoming email will not stay in your Inbox.
This is to ensure that your mailbox has free spaces.