Stone dildos have been recovered during archaeological digs. Dildos in one form or another and have likely been present in society throughout history.
What is a dildo
Various authors who have written about sex have their own ideas about exactly what is and is not a dildo. There is general agreement that a nonvibrating device, resembling a penis in shape, size, and overall appearance, is a dildo. Some authorities include vibrating devices. Some might exclude penis prosthetic aids, also sometimes called "extensions." Some might include penis-shaped items clearly designed with vaginal penetration in mind, even if they don't look very penile. Some authorities include devices designed for anal penetration (butt plugs), while others do not.
Early dildos were made of stone, wood, leather, or pottery. Of these, leather dildos with a fairly solid filler of cotton rag remain popular with some people. Rubber dildos, usually incorporating a steel spring for stiffness, became available in the 1940s. This was a less than satisfactory arrangement because of the potential for serious injury from cuts from the spring, when the rubber finally cracked and came apart. Later, PVC dildos with a softer PVC filler became popular. Most of the inexpensive dildos sold today are made this way. Chrome-plated steel dildos have been made, and have a small following, especially in BDSM circles. They are not particularly comfortable because they do not flex. In the 1990s, silicone rubber dildos became more popular, a trend that has continued as the price has come down. These are easier to keep clean and do not have the characteristic plasticy aroma of PVC. They were expensive when introduced but are now reasonably priced, making them an excellent choice for the first-time user. More recently, dildos made of borosilicate glass (Pyrex) have come on the market. They are expensive, and inflexible, but have a following. Other materials have been used as well.
Vaginal penetration is the obvious use. Dildos have fetishistic value as well, and some couples use them in other ways, running them over the skin during foreplay for example. If of appropriate sizes, they can be used as gags, or for oral penetration or a sort of artificial fellatio, or for anal penetration. Dildos are used by people of all genders and sexual orientations, alone or with others.
Safety and health
Some larger dildos are intended for visual appeal only and should not be used for penetration. Dildos can transmit disease between users in the same way as other forms of sexual contact, and should not be shared among users where this is a concern. This is particularly true for dildos made of porous or micro-porous materials, such as most soft synthetics. On the other hand, smooth stainless steel or Pyrex dildos are easier to clean, non-porous, and can be more easily sanitized, either chemically or by boiling. This is not meant to say that any unprotected dildo should be used by more than one person without being sanitized. An effective remedy is to use a fresh condom on the dildo. Dildos without a flanged base or other mechanism to control the depth of insertion should not be used anally, because they can be difficult to retrieve without medical assistance.
There are double-ended dildos of various shapes, intended mainly for use by two women. There are double dildos, with different-sized shafts pointing in the same direction, used by women to accomplish both anal and vaginal penetration at once. There are dildos designed to be worn in a harness, sometimes called a strap-on harness or strap-on dildo, or to be worn inside, sometimes with vibrating devices attached externally. There are inflatable dildos.