On line Gaming!

Please could someone explain to me what online gaming is. I am getting worried because we have the £17.99 package from Wanadoo and I use the computer for surfing a lot as does my daughter. My son plays an on line game called Guild Wars but when I ask him how long he plays it online he just says it is called Streaming or something so its not on line all the time. I am worried that we are overusing our connection because he didnt have this game in August when we went over to broadband but I dont want to stop him using it if he is not using the internet a lot for it. I am confused by this

When your son is playing online he is conected to the game server and every so often information has to pass over the internet to update the game so it a progress.

It needs to do this to know where all the players are and what they are doing otherwise what is the point of playing online if you don't know where the ppl are your playing with the info that is past is the stuff to say where ppl are bu the main stuff like backgrounds and the like are in the game and on the pc 's harddrive and it need to talk to the game server to get the right background for the game that is being played.
I don't think that he would but your connection at risk Foxy as the info is very small that is past over the internet it is not like a first person shooter where you need alot of updates as the game goes along.
My sonplays alot of first person shooter games and i can tell when he's playing online cause he takes alot of bavdwidth and slows the connection down because of the amount of information that is being passed over the internet to the game server.

Oh thanks Leo for explaining all that I have just upgraded to the next package though of £22.99 just to make sure because I do spend a lot of time on line especially at night and I think we were over our limits anyway.