Another difference between SEM and SEO is that you can launch an SEM campaign in a relatively short amount of time and have your ads shown at the top of a search engine results page (SERP), but with SEO you have to have your web page crawled, indexed, and ranked and then there is no guarantee the search engines will like or display your listing where it can be found (new websites sometimes take months or years to earn a valuable first-page ranking).
How SEM and SEO results are displayed also differs greatly: SEM results are ads which can appear as shopping ads (usually at the very top of the page showing individual products) or listings at either the top or the bottom of the SERP. These ads have several different configurations which may include information at a store’s location, links to different pages on the advertiser’s website, the website link, a phone number, a review ranking, a discount, and potentially even a form to fill out.
SEO results usually follow a more similar format of having the web page’s headline, name of company, description of the page content, and the website link. SEO results may also include a map of the business’s location along with other similar businesses, more detailed information about a business including photos, reviews, phone number, links to social media profiles, and even the ability to purchase online or place an order.
Another key difference in SEM and SEO is that with SEM you can frequently (and dynamically) change your ad copy and test which ad copy works the best, while with SEO your ad copy is what got you the ranking and if you change it the ranking will adjust accordingly.