Fetch user plotted latitude and longitude on Google Maps

Fetch user plotted latitude and longitude on Google Maps

I've a map displayed to the user, and he/she has the ability to plot on
the map his/her location and the google map marker appears, now how do I
fetch programatically the location plotted by the user on the google map.
I will be using this data and storing it in my database, which I can
handle on my own, but I'm unsure of how to fetch the data plotted by the
user.
Someone has already implemented it or has a link or tutorials to it,
please share.
Thanks