Information that we can access and retrieve after long periods of time must be stored in the long term memory. Transfer to long term memory involves a process known as long-term potentiation. Neurons, the nerve cells in the brain, are connected through circuits known as neural networks. These networks represent complex information storage and brain function. When information is used or repeated consistently or many times, these neural networks are used more and more, and subsequently strengthen the more they are used, which is long-term potentiation. Long term potentiation allows information to become encoded long term by strengthening the neural networks.
Long term memory can last years or a lifetime and has an immense storage capacity. Loss of information from the long term memory occurs when the neural networks cease to be used and they weaken, or when they are written over by new networks. Information is remembered better the more frequently the neural networks are strengthened, hence why repetition of information helps with memory.
Long term memory can be divided into explicit (declarative) and implicit (procedural) memory. Explicit memory is the memory of specific pieces of information such as facts and events, that can be consciously recalled. It is primarily stored in the temporal cortex area of the brain.
This is further divided into episodic memory, the memory of experiences or personal events, and semantic memory, the memory of impersonal facts.
Implicit memory is unconscious memory of physical skills or actions such as riding a bike. These memories are primarily stored in the cerebellum and motor cortex.
Another division of long term memory is by time period. Retrospective memory is the remembering of past information, such as dates, people, events, etc. Prospective memory is the remembering of future information, such as remembering to do something.
Remembering that you received an award four years ago is an example of retrospective memory; remembering that you need to water the garden is an example of prospective memory. Long-term memory allows people to store important information for long periods of time.