The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
LocationShare is a simple way to tell someone exactly where you are. This can be simply done by opening the application and waiting for your iPhone to get your location. Send your location by E-mail of SMS. This is received by the person you send the message to and as long as they have LocationShare installed on their iPhone, it will open the application, they click on 'Show Map', and they will see their current location and your location.