Internal monologue, also known as inner voice, internal speech, or stream of consciousness is thinking in words. It also refers to the semi-constant internal monologue one has with oneself at a conscious or semi-conscious level.
Much of what people consciously report “thinking about” may be thought of as an internal monologue, a conversation with oneself. Some of this can be considered as speech rehearsal, and it seems to be that the internal monologue is generally in the native language of the person concerned.
An internal monologue may be consciously used in order to organize thoughts to solve problems or keep track of a long list. More mysterious is subconscious internal monologue, which is thought to be used in long term memory and dreams.