You have been able to search for YouTube videos whilst in Google Maps for a while now but until now YouTube has not had its own geographical search feature. This means that in the past when you searched for say Paris in YouTube you would be shown hundreds of videos by someone called Paris Hilton (who my girlfriend informs me is not actually a hotel in the French capital).
Now when you search for Paris in YouTube a small map appears next to the videos of a scantily clad woman.
When you click on the map you are then taken to a larger map with a red polyline circle. You can move the circle around or you can zoom in to focus on a smaller area and YouTube will look for videos geo-tagged in that area.
This is an excellent addition to YouTube. It has been one of my biggest bugbears with the site that a search for a geographical location often returned videos that had no relation to the actual place.