Telenav is a navigation app for your phone. The link sends you to the free, no cost app for your phone. There is a subscription-based program too that you can enable from inside the app - the subscription-based program includes lane assist and a few other goodies, but nothing really worth the extra monthly fee in my opinion.
Edit: This version of Telenav does not download maps to your phone. I was under the impression that it would allow real-time mapping when leaving data-enabled areas, but it does not. If you want an app that will do that, I would recommend CoPilot Live from the Market. Telenav is simply a navigation replacement for Google Maps if you do not like to use that application. Sorry if I misled anyone.