The International Drivers Permit or IDP is simply a booklet with translations in various language of your own driver license. It always needs to be shown together with your original drivers license.
If it is connected with your own license, why does an IDP always have a very limited validity (1 year)? Wouldn't it be logical to use the same validity as your own license? The terms in your license don't change, so why need a new translation document every year?