This infographic goes into more detail about search engine optimization (SEO), pay-per-click (PPC) advertising, and search engine marketing (SEM).
What's the difference between SEO, SEM, and PPC
SEM is probably one of the most commonly misunderstood terms in digital marketing. SEM is not SEO. SEM is not PPC. It’s the net effect of both.
SEO is the technical organization of a page or post so it ranked higher in the search engine’s algorithm. While there is no official documentation about how these ranking algorithms work, experts agree that rankings are driven by five key elements: relevance, page quality, keyword use, domain authority, and mobile usability.
Relevance is an algorithmic measurement that guesses how relevant a given page will be to a reader who just entered a search term or keyword. Page quality has to do with the technical aspects of the page. Keyword use looks at the number of times that a given keyword is used in the text. Domain authority is street cred. It’s generally measured by how many people link to you. Mobile usability is also linked to the technical aspects of the page.
PPC is also affected by some of the same factors. Therefore the price you pay for a certain keyword or how often your ad is served to your audience is also based on relevance, quality, keyword density, etc. This is why it is so important to have a coherent keyword strategy. It is critical for both of the elements of SEM.