I hear these terms used interchangeably all the time but they are actually very different animals. While no one would ever accuse me of being a grammar snob, I do want to make the distinction because I want my clients and potential clients to understand that I can help them organically optimize their blogs, but I won’t be much help with their paid SEM campaigns.
Here are my definitions:
Search Engine Optimization (SEO) is the art of optimizing one’s website, blog, or press release so it will be read, indexed, cataloged by the search engines and subsequently returned in SERPs (search engine results pages). Preferably on the first page of Google, in the #1 spot! This is done through the use of site design, key word optimization, image tagging, and more…much more. THINK ORGANIC!
Search Engine Marketing (SEM) is any activity that increases search engine ranking including PAID programs like Pay-per-click and Google Ad words. THINK BIG BUCKS$$!
Personally I prefer the organic method. It takes more time, but is better for your pocketbook and may just get you to write more intriguing content.