Appointment Booking Website

Good day, this question is not about any Codecademy project but recently I began working on a personal project which is an appointment booking website for a business service. And based on my knowledge on html, CSS and Java, I was able to construct a visually appealing website that functions almost 100% as intended however, I’m quite unsure as to how to link the website with an email or phone number so as to send notifications once appointments have been made. Could someone be so kind as to direct me on the right topic to read up on to fulfill such actions