A preset is a pre-defined set of rules that can be enabled or disabled at any time. Presets allows you to pre-configure rules for your incoming numbers and then activate these rules when they are needed. For example, you may have a rule which sends all your calls to a mobile or straight to voicemail at the click of a button.
When you first visit the presets page, you'll see a list of presets already configured in your phone system:
Each preset will show its name, any associated numbers and a status button. If the preset is currently disabled, a green Enable button will be disabled, and if it's enabled an orange Disable button will display.