This feature allows you to attach an auto follow-up sequence to an email you sent via Gmail.

You can attach an email sequence to any draft – for example when sending meeting minutes after the sales zoom meeting you probably want to set up the automatic auto follow-up. Just enable Auto Follow Up in your Gmail, compose view and select the template (template is basically a list of pre-canned emails):

And if even if the email is already sent, you can still attach an auto follow up sequence to it: select the email messages and chose the Auto Follow Up template: