Welcome to the wild, wild world of sex toys.
Sex toys are amazingly diverse – and basically, if you can imagine it, someone's found a way to make it real. (Or is working on it in a tool shed or laboratory right now.) The only limits to the variety and utility of sex toys are the laws of physics, the limits of the human imagination, and in some cases, battery life.
While a lot of people think that sex toys exist purely as aids to masturbation, it's a mistake to lump all sex toys into that category. While there are some that are purely designed for that goal, the overwhelming majority of sex toys can be used to enhance sex play between couples (or larger groups) by adding variety and breaking up stale routines.
In this sense, a sex toy is anything that helps to spice up your sex life. Sexy costumes, and even lingerie, although more clothing than toy, can still be 'toys' in this sense: they're a little something extra that adds a little something extra to your sex play, regardless of what they might be.
It's a popular misconception about sex toys is that they're all either vibrators or dildos. Nothing could be further from the truth. Sex toys come in a wide variety of types, although they can loosely be divided into two categories: those that are intended to take the place of a second person in sex, and those that are not (although for obvious reasons, most of the sex toys that fall into the latter category are pretty much in both categories).
Sex toys that are intended to replace other people include dildos and vibrators, but also such things as inflatable sex dolls and fleshjacks. The one common trait that unites all these sex toys is that they are intended to replace the body of another person, by simulating either the whole body or just the sexual organs of the body.
Dildos and vibrators also fall into the category of sex toys that can be used in couple (or more) play. In fact, there are some who would say they're better used this way – in your own hand, a vibrator might not be able to get to those hard to reach places, but in another person's hand, that can be greatly simplified.
In addition to penis simulators, there are also a wide range of other sex toys. These include the wide panoply of toys used in BDSM, such as whips, paddles, hand cuffs, restraints, blind folds and the like, all of which are more safely used with another person than solo.
There are also accessories, that, while not strictly speaking sex toys, do their bit to help things along. These include coverings for beds and the like (to save on cleaning and the attendant stress related to it), and even additional cushions, bolsters and other furniture that can make it easier to comfortably have sex in certain positions by giving support to the body of one or the other participant.