Google Latitude is a Geo Broadcasting software or a location aware app which tells your friends your current location. Inside the app you can send invitations to your friends to join Latitude using their Google account.
Latitude is integrated in the new Google Maps which makes it very powerful or accurate. Keeping up with people's preference Latitude has several privacy setting which allows you to choose if you want to tell your friends where you are or to keep your location private. I love the fact you can even set different levels of location sharing among your friends(best available location, city level or hide).