In Google map How to create custom area boundaries and check if given coordinates belongs to that area

I would like to define custom boundaries. E.g. would like to divide city in multiple areas say Area1, Area2 and so on.
I would like to save those custom areas in my DB and do search based on my DB data for area.

I know using draw line I can create Polygon.
I would like to check given coordinates belongs to which Area.

Is the draw line created polygon is best approach to create custom area boundaries?
How can I check whether given coordinates belongs to that area (Polygon) or not?

I have created polygon using draw line option of google map.
I am able to export KML file.

Not able to confirm should I save that KML file in my DB? Is it right approach?
Not able to check whether given coordinates belongs to custom areas.