Today, however, SEM is used to refer exclusively to paid search. According to Search Engine Land, Search Engine Marketing is “the process of gaining website traffic by purchasing ads on search engines.” Search Engine Optimization, on the other hand, is defined as “the process of getting traffic from free, organic, editorial or natural search results.”
Consider the age of your business. If you just opened your business and launched your website, it’s going to take time to develop your SEO and begin to appear organically in the search. While that doesn’t mean you shouldn’t put together an SEO strategy, it does mean that you could benefit from an SEM strategy until you build your SEO. SEM is an effective way to drive traffic while building organic SEO.
The key distinction is that SEM is a broader strategy which combines paid search and SEO tactics. So, if you set up a PPC advertisement, but don't take steps to optimize the ad or the website it links to, this is a standard example of paid search. However, if you optimize your site and your search content with solid keywords, then you put money behind it to boost it on targeted audience's search pages, then you're dabbling in SEM.