This knowledge base article details different ways of using the delivery time optimization workflow action for batch / one-off email sends. This would include any type of email like newsletters, webinar invites, promotional offers, etc. All in all, any emails you are sending that have a defined timeline to be delivered and are not part of an ongoing automated campaign.
Delivery windows can be as short as one hour and as long as seven days and anything in-between. In most cases, we recommend using a one day (24 hour) delivery window. Once a delivery window is set, the system will pick the best time for each individual to receive their email.
You may also want to check out this support article which reviews a number of frequently asked questions.
If you are interested in the different throttling options available to you, please check out this support article.