It’s easy to get confused about SEO vs SEM. Most professionals who work in search marketing know roughly what both terms mean, but how many of them can articulate how the two diverge?

Let’s explore the ways in which these similar yet very different disciplines interact and ultimately complement each other in any marketing plan.

What is SEM, really?

Search engine marketing, or SEM, is meant to cover both search engine optimization (SEO) and paid search, also known as PPC (pay-per-click) or CPC (cost-per-click). From enhancing content with organic keywords to making sure a landing page meets Google AdWords quality guidelines, any optimization for the web traditionally fell under the umbrella of SEM. Over time, though, SEM has come to mean something much more specific. Popular usage now covers paid search exclusively, with SEO separated out. SEM still refers occasionally to paid search with a minor emphasis on SEO, but that’s even rarer than using the term properly. For clarity’s sake, I’ll replace SEM with “paid search” for the rest of this post.

But aren’t SEO and paid search basically the same?

The short answer is no. In the world of digital marketing, SEO and paid search are more like cousins than siblings.

A solid SEO strategy and a strong paid search strategy should work together seamlessly to cover each other’s weaknesses. But they don’t affect each other directly because they focus on different factors influencing search engine performance.

For example, a website can have a fantastic SEO strategy and a nonexistent paid search strategy, yet still experience a measurable increase in organically driven visits over an extended period of time. More than likely, this site will miss out on the greater variety and number of customers that a paid search campaign could generate, and growth will be fairly slow.

On the other hand, a website can have a fantastic paid search strategy in place and experience short-term gains in traffic and click-through rates (CTR) while missing SEO optimization completely. In this case, growth will be fast and visitors/clicks will be generated through a more diverse set of keywords—but it may cost quite a bit of money that would be more effective elsewhere.

Ideally, a site should have both a well-thought-out SEO strategy and a planned paid search strategy to cover the most search real estate.

So how are they different?

SEO focuses on organic search results: the results generated by Google, Bing, Yahoo, and other search engines that aren’t marked as ads, including local mapping. Paid search, on the other hand, focuses on a bidding system where the highest-paying advertiser gets the most prominent ad placement and is charged a fee every time a user clicks on the ad. The real question, then, is not how the two methods differ but what kind of results each one produces.

Fishing is a handy analogy here. Paid search is like heading out with your fishing rod and dropping bait in the specific spots where you’ve heard there are fish. SEO, on the other hand, is like dropping a net in the river in the general areas where you’ve heard the fish are jumping. Both techniques catch fish, but not in the same way.

Paid search is precise and agile. You get the searchers you want, but you pay for that convenience. SEO is technically free, but it takes research and effort to make sure your net is in the right place and catching the right kind of fish. It also takes longer to move a net than to pack up your tackle and try another lake, and the same is true for drastically changing an SEO campaign versus changing a paid search campaign.

Why does any of this matter?

The impact on your results. It’s not a good idea to expect fast results from an SEO campaign, and it’s not fair to expect long-term results from a paid search campaign without investing enough in it. When employed correctly, SEO and paid search will fill in each other’s gaps and shore each other up with their strengths. SEO is ideal for branded keywords once a brand is established, whereas paid search is ideal for one-off advertising campaigns, such as a special deal with a specific expiration date. It pays to know which tactic you need for your digital marketing campaign.

The impact on who you hire. If you’re looking for an SEO specialist and using SEM terminology, you’ll be inundated with applicants who have more experience with paid search than with SEO. You may also find an SEO pro with paid search experience, but I don’t recommend having a single person handle both. For the best results, you need to focus on one or the other. Some specialists can compartmentalize and not let paid and organic-keyword research taint each other, but many have trouble—upping the risk that your pair of keyword strategies will meld into one.

If you’re the type of person who would rather not know how the sausage gets made, and all you want is a lone specialist to produce results, that’s fair. At least you’ll understand from the get-go how each of these search methods can help produce the results you want.