There are obvious differences between LTM and STM. First of all, the difference is in amount of information, which these types of memories can store. STM can keep quite limited amount of data, which remains in active condition for prompt usage. LTM can keep huge amount of information for very long time.
Besides, both forming and operation of STM are connected with momentum. We keep in STM some piece of information, some reaction, emotion, etc., which we have learnt or experiences recently, right at the moment. That is why in many situations information in STM is clearer and more detailed, than the one we can recall from LTM, which was recorded and stored long ago.
But, of course, STM and LTM are closely related between each other; because both of them (operating together) form our memory and allow us enjoy all its advantages. First of all, all the received information, which is kept in STM and used by our working memory for some urgent needs, sooner or later is transferred to LTM and gets stored there in order to be recalled in the future when necessary.
Besides, in many cases we find the information to keep in our mind for some urgent use (STM) in our old memories (LTM). In other words, sometimes necessary information for STM is recalled from our LTM. For example, a person can restore some vocabulary and knowledge of foreign language, which were obtained much earlier, and start practicing the language again, if required.
Memory is one of the most important functions of human brain. Memory is our ability to keep in mind and recall different types of information, which we receive from the outside world during out lifetime. Human memory depends on specific abilities of an individual, and also on the types of information, which has to be remembered. Biochemical structure and processes, which make human memory work, are very complex. Therefore, a number of memory related issues still remain not very clear for modern scientists.