Persistent Browser Based Games

A persistent browser-based game, or PBBG, is a computer game that satisfies the following two criteria:

1. It is browser-based. The game is played over the Internet using only a web browser.
2. It is persistent. Progress in the game is achieved over multiple playing sessions.

PBBGs merge the depth and longevity of an application-based game with the accessibility and portability of a browser-based game. PBBG can be spoken as pee-bee for brevity.

Excerpt originally from  http://pbbg.org