Activity Templates allow you to create predefined text that you can pull into Activities when first creating them.
Creating Activity Templates
These templates are plain text and can be managed in Tools & Settings > Customization > Display Settings
Use the New, Edit and Delete button above this this to create new Activity Templates:
Apply a Template to an Activity
To apply an acitivity template, simply create a new activity and select the template from the drop down list provided:
This will populate the Activity Note field with the standard text allowing you to edit or add to that standard note: