The three phases of the human memory are sensory memory, short-term memory, and long-term memory. This division of memory into phases is based on the length of time of the memory. Sensory memory is instantaneous memory. It is an image or a memory that enters your mind only for a short period of time; it comes and goes in under a second. The memory will not last longer than that unless the information enters short-term memory.

Information can be held in short-term memory for about 20 seconds or as long as you are actively using it. If you repeat a fact to yourself, that fact will stay in your short-term memory as long as you keep repeating it. Once you stop repeating it, either it is forgotten or it moves into long-term memory.

Long-term memory is the huge memory tank that can hold ideas and images for years and years. Information can be added to your long-term memory when you actively try to put it there through memorization or when an idea or image enters your mind on its own.