Indigestion can also be called dyspepsia.  It is a very general term for pain and discomfort in the abdominal area.  The causes for indigestion are widely varied.  It can be as simple as difficult to digest food or excess stomach acid.  If that is the case, then eliminating the excess acid can help.  Antacid tablets and things like milk of magnesia are basically alkaline in nature.  That is to say, they are chemical bases that neutralize the acid in the stomach.  For more serious and recurring indigestion, taking a medication such as a proton pump inhibitor can help.  This helps the stomach to produce less acid at the biochemical level.  Even more serious indigestion can include the possibility of ulcers or even stomach cancer.  Cures here are obviously more drastic.