Search Engine Marketing (SEM) is one of the popular Digital Marketing methods. SEM is actually a combination of Search Engine Optimization and Pay Per Click. SEO is about organic position on search engines that bring traffic overtime. It offers long term results and also online going process. It improves online visibility. It can also be free or low cost marketing. PPC is basically paid position that brings immediate traffic and immediate results. You can do it only when you spend money. It is one tome set up but also improves sales. If you want to improve sales and traffic, you will have to use a combination of both.