How does SEM marketing work?

There are two main types of search engine marketing: paid and unpaid. Paid search engine marketing is also known as pay-per-click (PPC) advertising, and it involves businesses paying to have their website listed at the top of search engine results pages (SERPs). Unpaid search engine marketing, also known as organic search or natural search, is the process of optimizing a website so that it ranks higher in SERPs without paying for placement.