I should also mention baking soda and baking powder shouldn't be used interchangeably because of the extra additives in baking powder (Not to mention it's usually much more expensive).
baking soda is the same as sodium bicarbonate. Baking powder is baking soda with a couple additives (corn starch and cream of tartar).
As far as why you would want to do this, baking soda can be used as an antacid. I'm unsure of why you would want to do it so many times a day (that equates in my mind like taking tums 2-3 times a day). Also you do need to be careful because stomach acid is supposed to be there and is supposed to be acidic. If you neutralize the acidity too much you could be setting yourself up for getting very sick.