Webmail is a Web-based email system. These types of server-based email systems are popular, especially with younger users. They offer a convenient alternative to email services that reside on a particular workstation, such as Microsoft Outlook, where getting email requires logging into a connection with the server and where emails are stored on site in the hardware storage drive.
Techopedia explains Webmail
Common examples of webmail include email services from Yahoo!, Hotmail, Gmail and other mainstream providers. Almost all of these email services are free and offer huge amounts of storage. That makes them extremely easy to set up and use. As experts have pointed out, there are benefits and disadvantages to these models. With webmail, the mail is always available through the dedicated servers over an Internet connection. However, with client-side email, old emails can be archived directly on the computer so that the user does not need an Internet connection to review them.
One of the other benefits of webmail systems is that they do not require the communications protocols that some resident systems do. Some of the less tech-savvy users who continue to use resident or non-webmail systems are frustrated by mail delivery failures that could be prevented by using a webmail product.