The term 'subconsciousness' is widely used to refer to the unconscious or preconscious mind, as described by Sigmund Freud, or the general concept of subliminal consciousness. It is also commonly associated with autosuggestion and hypnosis. However, due to its imprecision, psychologists now generally avoid using this term. Subconsciousness is the idea that encompasses the mind that lies beneath the conscious level and above the unconscious level.
The conscious mind cannot always process disconnected information, as it would be an overload of data. Therefore, the subconscious mind stores this information where the conscious mind can access it when needed for survival (or for other purposes, such as solving puzzles). For example, a person's conscious mind may have heard the words 'I promise I won't hurt you', while their subconscious was quickly assessing the situation and understanding why fear was present. The misuse of 'subconscious' and 'subconsciousness' has an exact equivalent in German, where the words used inappropriately are Unterbewusst and Unterbewusstsein.
However, upon reflection, one may realize that this feeling comes from an unconscious resentment of another person's opportunities and privileges at a younger age. Contrary to popular belief, 'subconscious' is not a psychoanalytic term. It can be derived through introspection and one can probably identify their behavior in a subconscious way, motivation or impulse. It is also assumed that the 'subconscious' contains (due to the influence of psychoanalytic tradition) any number of primitive or otherwise rejected instincts, impulses, desires and thoughts.
The subconscious mind stores information that the conscious mind may not immediately process with full understanding. However, it stores this data for later retrieval when remembered by the conscious mind or an astute psychoanalyst who can extract the information stored in the subconscious and bring it to an individual's awareness. The visible is conscious, while what lies lower and deeper are the subconscious and unconscious. Although these two together are much larger than what can be seen with the eye, they both exist beneath what is easily noticed.
In short, with some introspection, one can probably identify where their thinking, drive or motivation comes from subconsciously. The subconscious mind is a combination of everything one sees, hears and any information that their mind gathers but cannot consciously process to make sense of it. For instance, Gavin managed to make her subconscious recognize a dangerous situation which forced her to act in order to save herself thanks to her basic survival instinct; making her aware that it was a subtle sign warning her.