As you read this article, you store the words at the beginning of each sentence in your short-term memory while you work your way through to the end, enabling you to understand the text.
Short-term memory acts somewhat like a gatekeeper between incoming sensory information and long-term storage. You are constantly bombarded by information, and the incoming traces from your sensory receptors last for just fractions of a second before they are lost. You don’t have time to process all of it; so short-term memory allows you to pass small amounts of important information in a temporary loop while your brain decides what to do with it.
Short-term memory has two major limitations; the first is that you can only store a small amount of information, and the second is that the memory decays over time. If you pay attention, your short-term memory can hold around four chunks of new information for between ten and 20 seconds, but if you are distracted, you will rapidly forget it all. Rehearsing the information inside your head effectively resets the timer and restarts the memory loop, allowing you to extend this time. A part of the brain called the hippocampus then decides which bits are important enough to be committed to longer-term storage, and the others are quickly forgotten.