Complex sentence: A sexual fantasy can be created by the person's imagination or memory, and may be triggered autonomously or by external stimulation such as erotic literature or pornography, a physical object, or sexual attraction to another person.
Split into simpler sentences: A sexual fantasy can be created by the person's imagination or memory. A fantasy may be triggered autonomously or by external stimulation such as erotic literature or pornography, a physical object, or sexual attraction to another person.