It's a google app, separate from google maps, named My Maps. This is the most awesome app ever. (I may say that about several apps. Many of them made by google actually. But I always really mean it.)
You can go to https://www.google.com/mymap and you can download an app for your phone. The two sync, of course, this IS google after all. :-)
It's really just awesome.
Here are a few of my public maps, to give you some ideas:
Pa Road Trips -
Columbia County Pa Covered Bridge Tour
The Pine Creek Rail Trail
Where to see the Elk Near Benezette Pa -
Other Uses -
My maps is also great for mapping out genealogy. I've traced where our ancestors have fought in the civil war, and some of their properties, etc, along with homesteads, graves and places to visit.
It's also useful for geocaching. Have you ever solved a BUNCH of geoart puzzles and then were not sure how to tackle them in a logical order? Plug all the coordinates into mymaps and it's easy to plan your route. :-)