Consumption is spending by households on goods and services, with the exception of purchase of new housing. An example would be a family purchasing a new washer/dryer.
Investment is spending money on capital equipment, inventories, and structures, including purchasing a new house. An example would be a retailer purchasing its inventory from a wholesaler.
Government purchases are spending money on goods and services by local, state, and federal governments. An example is the salary of government workers.
Net exports are spending on domestically produced goods by foreigners (exports) minus spending on foreign goods by domestic residents (imports). An example is American car purchases by the Japanese compared to Japanese car purchases by Americans.