Eggplant, also known as aubergine, is of the same plant family as tomatoes. Like tomatoes, while they are sold as a vegetable, botanically speaking, they are fruits (specifically berries). Most commonly found in the market are the large dark-purple skinned variety; however, more and more varieties are creeping in. There are white specimens, the long and thin Asian eggplants, and miniature varieties as well. Regardless of variety, choose eggplants that are tight-skinned and that feel heavy for their size. They are fairly perishable and taste best when eaten within a day or two of purchase.
Eggplant can be prepared in countless ways. It can be breaded and fried as with eggplant parmesan. It can be roasted and turned into baba ghanoush or fried and turned into caponata. My favorite way to prepare it is to “pickle” it using this recipe from Michael Chiarello. There are a few things about eggplant that can be off-putting. First, they can be bitter. The solution is to salt the eggplant. As I understand it, the bitterness is in the liquid which is drawn out of the eggplant by the salt. Cut it as the recipe directs (slices / chunks / halved) and liberally salt the cut sides. Leave it sit in a colander for the requisite amount of time (usually about 30 minutes, but depends how big your eggplant pieces are). Once the liquid has been leached out, rinse the salt from the eggplant and use as needed. Another sticking point is that eggplant is notoriously capable of absorbing mass quantities of oil into its sponge-like flesh. This is also somewhat combatted by salting. By salting the flesh, you’re effectively breaking down the structure that allows it to absorb oil. A final note - eggplant are gentle creatures and need to be treated as such. They bruise easily, and discolor rapidly once cut. It’s best to not cut them up and salt them till just before you’re ready to use them.