Distribution lists are an easy way to send out training posts to a designated list of people.
It is not necessary for you to have a distribution list in order to send out training posts. You can still type out the names or email addresses of the people/contacts you would like to send your posts to. However, if you plan on repeatedly sending the same group of people/contacts training posts, these lists will make the process much simpler.
Another great thing about distribution lists is that you do not have to wait for your contacts to register before sending them training posts. The email notification will serve as a reminder for them to create their account and begin their training.