Internal marketing implies that a company is informing its customers about the objectives and strategies of the company and at the same time testing their product internally and getting reviews. When you are marketing generally, it means that you are briefing your customers with the product details and giving them information, in this case your customers are nobody else but your own employees. For instance, if a company wishes to test the smartphone they are about to launch and if people will find it useful, interesting and unique or not then they can give samples to their own trusted employees to get right feedback and suggestions.