Memory is divided into three stores: sensory memory, short-term memory, and long-term memory.
Atkinson and Shiffrin (1968) claimed that information enters sensory memory and only lasts for approximately 200-500 milliseconds before fading. However, the information will transfer to short-term memory if strong and deliberate attention is paid to it.
George A. Miller (1956), a cognitive psychologist, provided evidence for the capacity of short-term memory, known as Miller's Magic Seven. He called it the Magic Number Seven. He discovered that most adults could store between 5-9 items from our sensory memory to short-term memory, which has about 18 - 30 seconds of duration and a limited capacity of 7 focal points, plus or minus 2.
If it passes the short-term memory test, the rehearsal process can begin, which transfers the learned skill to Long Term memory. Without rehearsal and strong, clear focal points, it is forgotten. The more something is rehearsed while having strong and clear focal points, the stronger the memory trace. Long Term Memory (LTM) is said to have unlimited capacity.