Since ancient history, people have been looking for a magic potion to stimulate their sex lives, whether by boosting one's sex drive, enabling an erection, lowering inhibitions, or in seducing a partner. Fertility aids factored in, too, although until modern medicine came in, it was assumed that plenty of sex would lead to procreation. Classic aphrodisiacs fall into three categories: drugs with actual physical effects of some sort, those with psychological effects, and magic potions that might work due to the placebo effect.
Some aphrodisiacs were associated with animals that appeared to have a good sex life. Some were plants that grew in shapes that resembled genitals, so they obviously had a purpose there. And some just make you feel good or made a potential partner happy to receive them as a gift. Hey, when your partner has a headache, anything that would relieve the pain will make progress. Substances that contained needed nutrients got their reputation as an aphrodisiacs by restoring overall health and therefore sexual ability. And some were just downright dangerous. That said, there are more supposed aphrodisiacs than can be enumerated in anything short of an encyclopedia, but you'll learn about an awful lot of them at Today I Found Out.