The term blanching refers to the technique of plunging a food, usually a fruit or vegetable in to boiling water usually until either it's color is set or the food has softened slightly. This takes anywhere from a few seconds to several minutes, depending on what is being blanched.
Then the food is removed and put into an ice bath to "shock" or stop the cooking process and to set the color.
Why do you use this technique? It makes it easier to peel the skin of fruits like tomatoes and peaches . It also enhances the color of vegetables like green beans, asparagus or broccoli.
It's also a good idea to blanch fruits or vegetables that you intend to freeze, because blanching inactivates the enzymes that promote spoilage.