The term "SEM" is short for Search Engine Marketing. It usually refers to paid ads, such as "click ads" - the sponsored links on Google and other search engines, where you pay a certain amount every time someone clicks on your listing.
SEO is Search Engine Optimization which refers to what has come to be called ORGANIC search engine listings - the listings you get because Google or other search engine evaluates your website as important for the search term.
Usually companies specialize in one or the other of these.
What's odd about that is they are not completely independent subjects. If you are doing a good job of SEO for a website, you will know probably 50% of what you need to know to do effective SEM.
Likewise, if you are running an efficient, effective pay-per-click campaign for a website, you probably now know half of what you need to optimize the site for organic search engine rankings.
That is, if you are experts at both subjects, which few companies are
And yes, at FastF we are experts at both. And more.
What no one talks about is the huge, vital areas of Internet marketing that aren't covered by EITHER of these terms.
Like what we call the Visitor Experience. In short, what happens once someone actually arrives onto your site? Most sites do a poor job of it and waste most of their visitors.
Then there's the various aspects of Market Research, Directory Listings and Reviews, and so on.
There's a lot to do to maximize your potential on-line. A LOT.