Short-term memory, sometimes referred to as "primary," "working," or "active" memory, is said to hold a small amount of information for about 20 seconds. Estimates of short-term memory capacity vary - from about 3 or 4 elements (i.e., words, digits, or letters) to about 9 elements: a commonly cited capacity is 7-2 elements. In contrast, long-term memory indefinitely stores a seemingly unlimited amount of information. Short-term memory can be described as the capacity (or capacities) for holding in mind, in an active, highly available state, a small amount of information. The information held in short-term memory may be:

- recently processed sensory input;

- items recently retrieved from long-term memory; or

- the result of recent mental processing, although that is more generally related to the concept of working memory.

The relationship between short-term memory and working memory is differently described by various theorists, but it is generally acknowledged that the two concepts are distinct. Working memory is a theoretical framework that refers to structures and processes used for temporarily storing and manipulating information. As such, working memory might also be referred to as working attention. Short-term memory generally refers in a theory-neutral manner to the short term storage of information. Thus while there are short-term memory components to working memory models, the concept of short-term memory is distinct from these more hypothetical concepts.

When trying to understand more about memory, it pays to first consider what the nature of memory is and also its various functions, as too the ways and means in which it can be used in our daily lives. Memory is a process by which a human being or other living organism can store and retain as well as subsequently retrieve or recollect pieces of information, and, in addition, it also pays to understand the working of memory and learn its various classifications that themselves are based on type of information, duration and also the methods by which they are retrieved.

Among the different forms of memory known to us, there is short term memory that is distinct from long term memory and also sensory memory. Short term memory is that type of memory that allows us to recall things from just a few seconds ago, or even from as long as a minute back, and it is also normal for short term memory to allow storage of just four or five objects, though this number may go up depending on what is known as ?chunking?. Thus, with chunking, when you see a group of letters ordered in rows rather in scrambled form, it allows us to remember those groups of letters a lot longer than in the case of merely scrambled letters.

When estimating the duration of time that short term memory can hold information, it is necessary to understand that there could only are three to four elements such as words, letters or digits that can be stored, though it could even increase to as many as nine elements, which is in stark contrast to long term memory in which information is stored and recalled over years, and the amount of information recalled can also be almost unlimited. In other words, it would not be wrong to describe short term memory as being the capacity for retaining in the mind which is in an active state a tiny amount of data or information that include things such as recently processed sensory contribution, information or items that were recently retrieved from long term memory and finally, they could be results of some mental processing that just took place, though this form of information may better by processed by working memory.

Furthermore, it has been found that all memories actually pass from short term memory to long term memory after the passage of a certain amount of time, though there is as yet no definite knowledge available as to how the mechanism that transfers information from short term memory to long term memory actually functions. Thus, it is safe to say that any tiny piece of information that remains in your mind immediately after you first encountered such information, is stored in short term memory, and all others are either stored in working memory, or in long term memory, or even in sensory memory.