Hi, Martín,
"A web-based application only needs you to have a browser"...
Since .NET Winforms (and VFP8, and other tools) can access/'consume' XML Web Services, an application *can* be web-based without utilizing the browser.
In this instance, you have another player in a distributed model, with a rich-client accessing a web-service as a portal. This model can work well with corporate users (both internal and remote) who have decent desktops/laptops, and where there's no issue installing the .NET framework.
I'm sure there are different perspectives on this, but I generally see two classifications of web-based apps (with respect to the UI): browser-based, and 'smart-client' based.
Kevin