Can anyone please tell me what is GPS tracking Application?

Since you posted this under cell phones, I would suggest it is an app that allows a cell phone to track another phone's location or to be tracked.

When asking question its better to give some context so we can help.

To further explain GPS stands for Global Positioning Satellites. It is a series of satellites in orbit around the earth that can read a signal from a GPS device and determine its location on the surface of the earth and then send back that info to the device or another device. The technology is very mature and loads of people have GPS navigation systems built into their cars or portable devices. Smartphones and tablets also have the capability now.

Works great, all parties have to have it on their phone and allow the others to track.
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But my wife and I knew were each other were at, and where our son was at any time

Hi both of my friend. I also read something about this. GPS tracker is used for recording your travels. People who have important statistics to know where they can improve like Hikers, cyclers, runners etc, this is a very good apps for them.

Secondly, more important is tracking our family, friends, loved ones and valuable belongings. Android smartphones are become cheap in price, so you can have one in your kid's backpack; track your pet with it or even your vehicle.

Thanks for your support.

Yes, they will do all of that, several get programs out there, but your phone will have to have those capabilities.

You asked what a Tracking App was, that is a specific item that will run on a GPS enabled smartphone or computing device.

But as I said, GPS is a mature technology. There are devices for hikers, runners and cyclists to log their travels. You can even share your routes on some websites.

These devices have been around for several years now.

I use a great app for cycling (Strava) and I use another for simply keeping track of the route I took on hikes (MyTracks). Both are free in Google Play. I also geocache so I'm quite familiar with GPS technology. I do NOT track anyone in my family nor do have I found a reason to allow Google's Latitude function - for privacy purposes.