GM is almost entirely related to automobiles;
GE's business covers many fields, from household appliances to aero-engines, to medical and health undertakings, and then to the financial industry. Recently, it is acquiring shares in SDB, becoming the second largest shareholder of SDB.
General Dynamics GDC is the largest military ordering contractor in the United States, mainly responsible for arms.
General Motors and General Electric are two different companies. It doesn't matter, but the name is similar. GM stands for General Motors and GE stands for General Electric.
General Motors is the world's largest automobile manufacturer, and General Electric is the world's largest cross-industry enterprise (everything from light bulbs to ships). Last year, General Motors ranked fifth among the top 500 companies in the world, and General Electric ranked ninth. General Dynamics is a subsidiary of General Electric Company.