Laravel allows developers to send notifications in their PHP applications using various channels such as mail, SMS, Slack, and database. To send notifications through WhatsApp, a custom notification channel needs to be created, which involves setting up the Twilio API for WhatsApp. The process includes creating a new directory for the notification channel, defining a message class, and implementing the sending of messages. Additionally, a notification class is created that will make use of the custom notification channel to send notifications to users when their order has been processed. The application can be tested by running it and clicking on the "Place Order" button, which should trigger the sending of a WhatsApp notification to the user's phone number.