Complex sentence: A sexual fantasy, also called an erotic fantasy, is a fantasy or pattern of thoughts with the effect of creating or enhancing sexual feelings; in short, it is "almost any mental imagery that is sexually arousing or erotic to (an) individual".
Split into simpler sentences: A sexual fantasy, also called an erotic fantasy, is a fantasy or pattern of thoughts intended or actually creates or enhancing sexual feelings. It is "almost any mental imagery that is sexually arousing or erotic to (an) individual".