Subconscious and Unconscious are words that can be used interchangeably. However unconscious was coined by Freud to denote that part of the mind we know nothing about that holds our repressed memories and ideas that shape our conscious behavior.
The subconscious used to describe those things we do without conscious attention to, such as riding a bike, driving a car, typing, etc.
“Subconscious or unconscious mind (terms which can be used interchangeably), is the part of our mind, which operates usually below the level of our normal consciousness. Like in the iceberg analogy, the subconscious mind is the vaster and more substantial part of our mind. Out of the 2 Million bits of information which approach us every second, the conscious mind can only register approximately 7 bits, whereas the subconscious mind computes around 140 bits per second. The subconscious mind is in charge of our emotions, which explains why we can feel a certain way without really knowing why – for example waking up grumpy one day and completely happy the next. The subconscious mind also stores memories from any events of our past.”
Our subconscious also controls all of our physiological functions of the body; we don’t regulate our heart rate, breathing, kidney function or digestion with our conscious mind.
Another spin is that we have a conscious mind, an unconscious mind and the subconscious is a buffer between those two. Along with these there is an intra-conscious that connects with the larger field of all knowledge. It has been maintained that we need to believe in this state to connect with it. Most people don’t and therefore never have any contact with this intra-consciousness.