Autoeroticism refers to a sexual arousal in the absence of external stimuli. This means that the sexual arousal is internally conjured via the imagination or "sexually neural" stimuli.
More About Autoeroticism
The most common form of autoeroticism is masturbation. Autoeroticism can include any internal sexual stimulation like erotic dreams or daydreams, too. Some use the terms autoeroticism and masturbation interchangably, but not all autoeroticism is masturbatory.
The topic of autoeroticism receives much attention. It is still unclear as to whether certain forms of autoeroticism (such as autosadism) is a form of sexual orientation, denotes a lifestyle choice, or simply refers to masturbatory practice.