Peaches and nectarines are summer's kissing cousins. In fact, they're so closely related that occasionally a peach tree will bear nectarines and vice versa. Essentially, the difference between the two fruits comes down to fuzz (botanists call it pubescence). Peaches have it, nectarines don't. There may be a slight difference in flavor as well. Peaches seem to have a muskier flavor, whereas nectarines tend to have a slight lemony note.
How to choose:
It's important to pay attention to color -- not the red blush, which is meaningless, but the background color, particularly around the stem. If you see some green, it means the fruit is not yet ripe. Leave it at room temperature for a day or two, though, and it will ripen just fine (don't refrigerate a peach or nectarine until it is fully ripe). Also pay attention to the quality of the background color. Most peaches and nectarines are creamy yellow; look for ones that glow an orange-ish gold, they'll be the sweetest and best-flavored.
How to store:
Peaches and nectarines will continue to ripen after they've been harvested if you leave them at room temperature. They should never be refrigerated until they are fully ripe. Chilling them before that will result in fruit that is mealy and flavorless.
How to prepare: