As others have stated, a shallow well gets water from the uppermost water bearing formation. Things to consider are activities around the well site which may contaminate the water by perculation and microorganism contamination which may have always been present yet causes problems for your family. Neither can be serious nonetheless you should be aware of such conditions to possibly eliminate the sources and keep your water supply fit for use. Relatively simple and inexpensive one-time lab testing can identify potential contaminants if concerned. Also, you can contact your local county health department to inquire what if any problems other well owners in the area have experienced i.e., contamination, seasonal shortage etc. Regardless, your well water normally will be better tasting than any treated water piped to your home. Hope this is information you were looking for.