Human memory can be divided into 3.
1. The Sensory Memory
2. The Short Term Memory
3. The Long Term Memory.

1. The Sensory Memory
The sensory memory is responsible for storing information for a short period of time, let say few seconds and it is not used during studying at all.

Let say I ask you to take a glance at the below numbers.
9, 5, 1, 3, 7

I now told you to close your eyes and think of other things without checking the numbers again, I now told you to write the number down somewhere in the right order.

Probably, you might not get it, but you will know the number involved, you will get the numbers but not the order, that's the power of sensory memory, just for few seconds.


2. Short Term Memory
The short term memory is formed from constant revision of what we stored in Sensory Memory, let use the number I wrote above as an example. If instead of taking a glance at the numbers, you read them to yourself again and again, probably, you will recollect the order.

Short Term Memory is used by students to prepare for exam, you will see that many students forget whatever they read after exam.

3. Long Term Memory
Long term memory is the real deal, constant revision of what is stored in short term memory transfered the thing into our long term memory.

And it will be hard to forget that.