Places is an iPhoto feature that uses location information to plot your photos on a map, so you can see your photos grouped by where you took them.
If your digital camera or iPhone has Global Positioning System (GPS) capability, iPhoto automatically maps your photos using that information (you can change your settings in Advanced Preferences to stop this if you want). iPhoto uses a database of locations to translate the GPS data into useful place names, such as “Grand Canyon.”
If your camera is not GPS-enabled or your photos don’t have location data attached (because, for example, you scanned prints into your computer), you can easily enter the location information for single photos or entire events.
You must be connected to the Internet for iPhoto to show your photos on the Places map.