SEO, or Search Engine Optimization, is actually one element of SEM, or Search Engine Marketing. Search Engine Optimization is the process of configuring, or optimizing your website with the appropriate keywords you wish to be associated with, in a manner that will make it easily "seen" by search engines. Some of the more common SEO tactics include:
1. Having Keyword rich web pages
2. Having Keywords in the title of your pages
3. Having Keywords in your domain name
4. Naming the images in your site using keywords
5. Naming the Alt tags of images using keywords
Search Engine Marketing is the process and the methods used to promote your site to search engines. The most common tools are:
1. Search Engine Optimization
2. Article Marketing
3. Video Marketing
4. Social Network Marketing
5. PPC, or Pay Per Click Advertising
In most of these methods, the idea is to generate high quality, relevant content that is keyword rich and placed on sites other than yours, This content contains back links that point back to your site. Google and the other search engines use these factors to rank you in the search results people enter. The more back links you have from original quality content, the more important and relevant you are to Google's results and page rankings.
The important parts above are that the back links to your site must come from relevant, original content. If you have used some of the spamming services or link farms to try to build your back links, Google may penalize you and possibly even black list your site.
Back links generated "Organically," meaning that they are from high quality, relevant content are also very important to Google, whereas Paid advertising - even Google's own PPC program - does nothing to help you get higher up in the page results rankings.
Reference Article : EzineArticles.com/?expert=Brian_Woeller