Lag

Summary
Lag, from "lag behind", is a slang term for slow internet speeds or internet latency; Lag is sometimes due to a server problem, but more frequently due to the connection between client and server.

Lag Slang
A lagger (occasionally, High Ping Bastard or HPB) is someone who uses a relatively slow 56 kbit/s modem to connect to the internet, then joins a multiplayer online game (usually a first-person shooter) and who therefore has a high ping time. In synchronous games, where all clients must know the exact game state, a single "lagger" will slow down the game for everyone, since the server has to wait for the client to get every communication packet. However, many online games use an asychronous communication model, allowing the clients to continue even if they drop occasional packets. A high-pinger who does not inhibit the overall performance, just his own, is sometimes known as a High Ping Bait.

Low Ping Bastard or LPB is a phrase that originated during the time when Quake was a highly popular multiplayer online first-person shooter. The term came into common usage when broadband Internet connections first came into the reach of home users and were competing with people limited to a 56 kbit/s or slower modem connection. This term was so widely used because of the havoc wreaked upon the other users of these servers by the LPBs due to their overwhelming advantage in reaction time afforded by their connection.

A 56ker is a slang term for a person using a 56 kilobit modem connection. These connections are considered to be slow compared to modern broadband connections and generally result in lewd complaints from other higher bandwidth participants in the game or channel.

Modding
Lag can be used in modding, Some mods are designed around lagging all the users except the modder out, But sometimes are caused by accident when a modder makes something spawn out of a weapon, and somebody uses that weapon a lot and spawns loads, this normally lags the modder and and forces him/her to restart his/her xbox as it crashes.