SharePoint: ExcuteQueryAsync functions inconvenient

Can any body explain this ?


clientContext.executeQueryAsync(
Function.createDelegate(this, this.onQuerySucceeded),
Function.createDelegate(this, this.onQueryFailed));

it always output an Error in on MSDN site sure i've something wrong it worked when i replaced with the functions like


clientContext.executeQueryAsync(function(sender,args){...},function(sender,args){...});

can anybody tell why ? and whats "createDelegate" ? and whats "this" ?

SharePoint