Getting into a translocation pod, which is like airplane's cockpit, you pilot a gigantic combat robot called 'Mech on the planet Solaris-VII in the 31st century. The opponents are not computer generated, but piloted by humans, who are in other pods just like you. This is definitely different from those arcade video games around. Up to eight people can be translocated to the same place at a time.
You can play BattleTech at Virtual World around the world. If you want to know more about BattleTech, KIM.EXE!!!'s BattleTech page would be helpful.
There are other kinds of BattleTech. One is a board game from FASA, the origin of this virtual world version. The other is recently released PC game version, MECHWARRIOR2 from Activision. Japanese version is also available.