About Lat, Lng and Bounds

The latitude specifies a location's distance north or south of the equator. The longitude specifies the location's distance east or west from an imaginary, arbitrary line connecting the North and South Poles. This line is called the Prime Meridian and passes through Greenwich, UK. Google Maps uses decimal degrees rather than degrees, minutes, and seconds. Precede South latitudes and West longitudes with a minus sign. Greenwich has a latitude of 51.4788 and a longitude of 0.00. A location to the west of Greenwich would be - x degrees, to the east + x degrees. The Eastern Hemisphere goes all the way around 180 degrees to the east (eg lng=22.837746), and the Western Hemisphere goes all the way around to the west 180 degrees (eg lng=-22.028). lat=90 is the north pole, lat=-90 is the south pole, lat=0 is on the equator.

Map bounds are two location points, bounds_ne and bounds_sw. NE is the top right corner of the map, SW is the bottom left corner of the map. Each bounding point consists of a latitude and longitude separated by a comma in brackets. bounds_ne="(48,-74)" bounds_sw="(42.4253710802915, -77.69776451970847)"

That depends. It will change depending on the size and shape of the displayed map (usually determined in turn by the responsive features of the site skin), and the address of the map location (and geocoded latitude and longitude). The map bounds will be visible but the actual corners of the map will be adjusted in order to best show the address, marker or markers for the display size and viewing device.

The zoom level is overridden by the more advanced use of bounds. You can specify the zoom level for the initial map shown in the item forms, but apart from that we use bounds because of the additional responsive and multi-marker features that they offer. Bounds are harder to get your head around, but they are far more useful. https://developers.google.com/maps/documentation/javascript/reference#LatLngBounds