Each and every PvP is a single player versus single player.
A "mass" PvP can be described best as a "Guild War".
A Guild War is 1 guild versus another where a group of players from each guild, in a given area, are allowed a free reign of terror. Free for all mass mayhem.
To request a Guild Vs. Guild, simply type "/guildwar "enemy guild name" "number of kills to win".
For example:
Afterwards, a message appears to the Guildmaster of the opposing Guild.
Note: Only Guildmasters can send/ recieve Guild Vs. Guild requests.
The first Guild to score "X" kills wins. Guildmasters agree on terms and conditions beforehand. The kill bar will move outwards from the middle, the first Guild to fill the bar with kills wins.
Honor points are gained when you kill and lost when killed. The Guild that wins gains bonus Honor Points.