Multiplayer is the server based part of Critical Strike Portable and Critical Ops which enables players to join different servers, work together or kill each other. This option requires a connection the Internet.
Critical Strike Portable
In both Single Player and multiplayer, gameplay is generally the same, but multiplayer has real-life opponents and allies, which can be useful for practicing, also assisted by a chat function (Y). When pausing, no game mechanisms stop when pausing the game. An enemy can still shoot a player despite them pausing.
Hosts can make servers and choose gamemodes for them. Hosts can also have access to server settings. Players also have the option to vote to kick a particular person (usually hackers). If the host leaves, the player that joined after takes over.
Currently, multiplayer is the only playable option for players to choose. Unlike Critical Strike Portable, server hosts do not have any server settings to edit. They and other users also do not have the option to kick other players.