SEM stands for Search Engine Marketing and you can now have a free analysis done by Apogee Search, one of the 25 largest Search Engine Marketing firms in the world.
I got to know about this offer while going through their Search Engine Optimization (SEO) page.
For your information, Apogee Search was launched in 1991 by early Internet pioneers and McKinsey & Co. alumni. They specialize in proven online marketing methods including paid search, affiliate marketing, etc. Their solutions are designed to drive qualified, targeted visitors to B2B and B2C websites for more leads, customers, revenues and profits.
In case you are scratching you head now it is clear that you are new to SEO and internet marketing. You might also want to check out the Search Engine Marketing Glossary on their site.