Stream of consciousness is a method of writing where you write down everything and anything that pops into your mind as you think. This method can be used to write entire novels. For example the method used to write Ulysses by James Joyce is stream of consciousness. I wouldn’t recommend writing your novel in stream of consciousness because it can often get difficult and confusing to read, and your readers will not be happy with you.
There are some instances where stream of consciousness is helpful. I use this method of writing to write ideas down so that I have all the information I need to transform the idea into a full-fledged story. I am not expecting anyone else to read what I have written in my notebooks so I refrain from separating my writing into paragraphs in my notebooks. This mostly helps me to develop ideas in my head without altering them too much. And if I need inspiration I can just flip through my notebooks to find an unused idea.