
People have two kinds of memory, a long term memory and a short term memory.
A long term memory holds ideas for a long time. For example, you don't forget your birthday.
A short term memory holds things for a minute to a couple of days, For example,you won't probably remember what you had for lunch a few days ago.
If you want to move something like a phone number from your short term memory into your long term memory, you can make what you want to remember into patterns or mneumonic devices (make up a little story or something.)