Any wireless controller should be sold with one of these as standard.
If you use a wireless controller on batteries, you'll end up spending far too much money, and when the controller runs out if on live, it could leave you getting killed and loosing points.
This comes with a wire, and a back.
The back goes where you have your batteries in the back of the controller, and once you put it in, it stays there for life.
Next you plug the wire into the top of the controller, not into the bottom. So you can charge your pad while you're playing your game, and have the headset in it at the same time.
Microsoft did annoy me with this though, when I bought my 360 I thought this would be included in it. It wasn't. Stupid microsoft.
But wireless is much better than a wired pad I suppose, so it is worth investing in this, it will save you money in batteries in the long term.
Also, there is no lag on the wireless, its just as good as a wired controller. You know when to charge it because the middle of the part has lights going around it, when they spin around that means you plug your wire into it, carry on playing while it charges, then when its charged you just take the wire out and enjoy the wireless gameplay.
Buy this, buy a wireless pad, and enjoy.