what is overiding , why and what is it used for.....


Here is some sample code that is confusing me....

Nothing new there then.... lol


public override string ToString()
{
  return "Name:" + Name "\nVal" + Val;
}


This is on page 243 of the book begging visua c# 2005

later we have console.WriteLine(myObj.ToString());

so what is called here the function above or method above
and can some one explain the reason for doing this.. why not just
write myObj.methodname() directly

like
public string methodname(void)
{
return "Name:" + Name "\nVal" + Val;
}