Maintenance Rehearsal is the process of repeatedly verbalizing or thinking about a piece of information. Your short term memory is able to hold information about about 20 seconds. However, this time can be increased to about 30 seconds by using Maintenance Rehearsal.
For example - late at night, you have been out partying all night, you get back home and you are hungry. you decide that it's time for pizza. So you pick up the phone and call information to get the number of a local pizza delivery place. When the operator gives the number, you say the number over and over so that you don't forget it in the time it takes to hang up and dial the number. This process of repeating the number over and over is maintenance rehearsal. It won't help get the information into long term memory, but it will help keep it in short term memory a little longer.