An information gap activity is a communicative activity where at least one participant (but usually all) is given information which their partners don't have. The pair or group then have to share the information in order to complete a task.
Examples :
Further Reading
Littlewood, W. Communicative Language Teaching, Cambridge
(Remember that Amazon will often have both new and used copies of the books you want at prices much lower than those shown here. it's always worth clicking to find out And no - we don't earn anything from your clicks!?