Some people don’t differenciate because both types categories “use video games for a purpose different that entertainment”. Well that doesn’t really help any professional: targets, clients and game mechanics are different so we need to differenciate!

Advertgames deal with sending a marketing message to customers, are mostly  driven  by advertising agencies (since they are marketing funded) and have been mostly stagnating at the bottom end of Flash. Serious Games are created with employees and stake-holders in mind,  directly bought by end -user companies and are growingly sophisticate.