ive heard about it and it illegal in the game but i dont know what it is and how not to do it

WorldSwitchers are generally where you can switch to a new world easier than using the main page. For example if you used the old SwiftSwitch there was a panel where you could click the world which you wanted to switch to and without going to the actual main page and then it automatically loading.

 

 

 

That is a simple explanation of a world switcher.

There is absolutely nothing wrong with normal world switching, it means logging out of a world, then logging into another.

 

 

 

Just use the Runescape website and applet and you've got nothing to ever worry about :)

He means the using illegal World Switchers as Geordiequeen explained.

 

 

 

You don't need to worry about it as long as you use the official client and stay away from bookmarking and clicking links to access worlds. And if you do use Swiftswitch, keep it updated.