[Soundy]

"How does it work" as in... how well does it work, or how does it actually function?

Geotagging is a pretty straightforward thing, and there are lots of methods to do it. Basic concept is, the timestamp on a photo is compared to the timestamp on a GPS track, so the coordinates you were at, at the time a photo was taken, can be determined and embedded in the photo's EXIF. A suitable mapping program or site (Google Earth, for example) can then attach the photo at the specific location. If you enable the proper layer in Google Earth, you'll see links to all sorts of user-submitted photos - zoom in on the Pitt River Bridge and you should see one of mine, showing a couple tugs working a log boom up the river.

GPSed.com has apps for Windows Mobile phones and iPhones that use the internal GPS in those devices, to record a track... phones with a data plan can then upload the track automatically at intervals for others to view. Later, the site can link to your Picasaweb or Flikr account for photos to attach to the track. They've done a great job of making it seamless and painless... and the service and software are free to use.