Optimizing a website in order to get traffic from organic search
Traffic and visibility from both organic and paid search
The goal of SEO is to rank your website in the website in the organic search results.
You can also get your website in the paid area of search results via Pay Per Click (PPC)
SEO is where you focus 100% on ranking in the organic results
SEM is when you tap into both SEO and PPC in order to get traffic from search engines
SEM is a broad term that includes both SEO and PPC which means SEO falls under the umbrella category of SEM
SEO takes time
When you stop paying, your traffic gradually reduces to ZERO