Hello. Note: I am a complete and total noob.

I am looking for direction in developing a Google API map that allows site visitors to insert information directly through the site. My idea is stemmed from this map here http://www.off-grid.net/landbuddy/

As you can see, a google map is visible and allows users to insert data such as location and description. They can even select a specific marker that better describes who they are. Can you please send me in the direction to figuring out how to do this? Perhaps a youtube video?