Search Engine Optimization(SEO):
It is the process of improving the volume and quality of traffic to a website from search engines via natural search results.
The purpose of SEO is to make the site better for both search engines and its users.


Search Engine Marketing(SEM):
It is about making your brand visible within the search engines to attract new visitors to your site. Its everything that can be done to utilize the technology of search engine to promote a website and increase its traffic, its stickiness. That's why SEO is a subset of SEM.

There are three main steps of SEM in search engine industry:
- Natural or Organic Listing
- Paid or Sponsored Listing
- Content Network Listing

Benefits of SEO:

Targeted traffic
Increase brand visibility
High ROI
Higher sales
Long term positioning
Cost effective
Accessibility
Usability
Cross Browser Compatibility

SEMPO:
The Search Engine Marketing Professional Organization (SEMPO) is an industry organization for search engine marketing firms. A non-profit professional association, SEMPO was formed in 2003, to promote search engine marketing and provide educational resources to members and consumers. Its sponsors include Google, Yahoo, Microsoft, SuperPages, and Search Engine Strategies. SEMPO's membership includes search engine marketing firms and consultants, Web developers, inhouse marketing professionals, and advertising agencies.