The multi-touch support on the iPhone provides a series of touch events consisting of smaller, individual parts of a single multi-touch gesture. For example, placing your finger on the screen generates one event, placing a second finger on the screen generates another, and moving either finger generates yet another.
One incredible example comes from Thomas Robinson ; he creates a virtual light table that pulls in Flickr photos, then uses multitouch to allow you to use two fingers to pinch, zoom, rotate, or simply move the images around on the screen (Figure 12–16).