If you are flying for hobby/recreation, then you really don't need to know what specific type of airspace you are in. You just need to know whether or not you are within 5 miles of an airport, whether or not you are in a restricted area, and whether or not there is a TFR in place where you are flying. If you are flying for hobby/recreation, then you need to notify the airport if you are within the 5 mile radius.
Attleboro appears to be within the 5 mile radius of Falls Pond Seaplane Base.
AirNav: 2MA7 - Falls Pond Seaplane Base
Otherwise, yes, it appears to be in Class G airspace. If you tap on the advisories in AirMap, you should see the specifics on the airport. Note that it won't show you the airspace class unless you select Part 107.
If you want to learn more about the specific airspace type that you might be in, check out SkyVector.
SkyVector: Flight Planning / Aeronautical Charts