There is a notable difference between an anal dildo and a vaginal dildo. A vaginal dildo or what you call the regular one, is meant to stimulate the clitoris or penetrate the vagina. An anal dildo, on the other hand, comprises a flared base so that it can enter the tight anus smoothly and without pain. Normal dildos usually do not have flared bases; hence, these are never meant to insert the anal area. Hence, sex toy buyers look for anal dildos, specifically when they have anal sex in mind.