Browser MMORPG games are a more recent way to play thanks to the evolution of web browser technology. These browser games utilize new browser technology which allow people to play without downloading any third-party clients.
Because of their cross-compatibility, these browser MMORPGs can be ported to any Windows PC, Mac, or Linux computer through browser support to allow for a much wider audience.
Just because browser MMORPG games are played within the browser does not mean their quality has to suffer either. New MMORPG games with advanced graphics can still have the same fidelity as their client-based counterparts.
The best part is most of these new browser MMORPGs are free to play, so you do not have to spend money just to download a game that you are not sure will work. Just open up your browser of choice (hopefully not IE) and let the gaming ensue!