Notifications are sent to your Host after a visitor has signed in. If the Host has an email address configured, an email will be dispatched. If the Host has a mobile number configured, a SMS (text message) will be dispatched. This email and/or SMS (text message) can be configured from the backoffice website as shown below.
Note that you can use placeholders in these notifications as described here: https://vizito.be/faq/20-badge-printing/6-which-placeholders-can-be-used