According to Google Knowledge Graph, SEO is the process of optimizing traffic to a website by appearing on the first page of a search engine result list, called search engine result pages (SERPs), during a search query. SEO is part of SEM.
SEM is a digital marketing strategy that uses paid and free advertising and optimization techniques to promote a website and increase its visibility in the SERPs. In addition to SEO, SEM uses the following tools:
– Remarketing
– Display ads
– Product advertising
– Pay-per-click (PPC)
SEO and SEM are intended to increase your website visitors by making your brand appear high in SERPs. Users are more likely to click on the top-half results of the SERP’s first page. One of the primary differences between SEO and SEM is that SEO is an organic approach, meaning it will naturally attract traffic to your website over time. SEM is a paid scheme wherein you will pay each time a user clicks your ads. Cost-wise, SEO is a better approach.
via business2community.com