“Webmail” is a term used to describe an email client which is accessed through a web page rather than as a standalone program.
Some well known services which offer webmail are services such as Hotmail, Yahoo, Gmail etc.
All versions of VPOP3 have a Webmail service included as standard.
With the default settings of VPOP3, you can access it by pointing your web browser at http:<address of VPOP3 computer>:5108. The default configuration of VPOP3 only allows access to Webmail from your local network, but you can configure VPOP3 and your router to allow access from outside.
See: VPOP3 Webmail Help