In order to understand the nature of the impulses that our mind reacts on to formulate our dreams, we need to differentiate the method of mental activity when sleeping and when being awake. When we dream we encounter many occurrences that are being conceived as realistic where in fact they are products of impulsive disturbances. These impulses mostly appear as visual images but with an impression that our senses and feelings are involved in these visuals. This is why we find it difficult to describe our dreams as these impressions come across stronger than the images and the images are difficult to be put into words. This non descriptive element of dreams gives as the sense of the bizarre and makes the research more difficult. On the other hand it is a common characteristic in all the dreams.
We can also examine some of the differences that Freud discovers in his journey for interpretation. The duration of the dream can vary from dream to dream. When we talk about duration we are not referring to the actual but the apparent duration; how long it feels for the dreamer and not the actual time that the dream lasts. It can seem to last as long as an image, a feeling or a thought where other times it could be an epic series of events with well-structured characters and incidents, more or less like a movie.
Dreams can also differ in precision. Now we talk about the impression of the dreamer when he is awake. More thorough dreams feel like real experiences in a way that their impression still lasts when we wake up. Sometimes we recall these dreams for the rest of the day as they left a very vivid impact. In this dreams the actions and incidents are quite clear for a conscious mind. Precise dreams are easier to describe. Other dreams seem very incoherent and make no sense in a conscious manner. They are often very difficult to put into words.
Another difference is the vitality of the dream and its impact for recollection. Some dreams could have a mix of vivid sequences with vague interruptions. Others could be consisted by very rational sequels in comparison to those that seem almost stupid and irrational. Some dreams may lack in the excitement of their content but the feeling that they produce could be perceived in such an intense way that it can never be forgotten. Childhood dreams often fall to this category. Depending on the gravity of their impression dreams are either easily forgotten or last for a whole day or a lifetime, or even fade slowly through time.
Frequency is another characteristic that is contradictory between dreams. The same dreams can occur repeatedly or they can differ slightly from time to time having a similar introduction and different storyline or a dissimilar content but always the same ending for example. Also similar characters or incidents can come back to completely different dream contents. There are dreams that can only come once in a lifetime.
What we can understand from these observations is that the external or internal impulses can make our mind react in a completely different manner each time we dream giving to the dreamer a huge range of images, apparent feelings or thoughts that can be put together in a non-linear manner combining different factors that affect their creation. There is no standard formula on the way the mind works in order to create specific dream contents. They are rather a synthesis of reactions that we are trying to examine closely by their differences and similarities in order to gain the knowledge of interpretation.