Search Engine Optimization is a process by which you make your web pages more search engine friendly in order to get the much desired higher page position. SEO is the process of improving your Web page or Web site in Serch engine. 

SEO = Search Engine Optimization,

* Getting your site ranked higher so more people show up at your doorstep.

What's the difference between SEO and SEM?

While some people use SEO and SEM interchangeably, SEO (search engine optimization) is actually a part of SEM (search engine marketing). 

SEO refers to the process of using on and off page factors (typically free) to get your web pages ranked for your chosen keywords in order to get more search engine traffic to your sites. SEM takes it a step farther to include using paid search engine listings and paid inclusion to get more traffic to your websites.

What's the difference between paid search and organic search listings?

Organic search engine listings are the main results users see when they do a Google search. The websites appearing in the organic listings appear because those sites are most relevant to the user’s keywords. Indeed, most of these sites appear in the top of the search engine results because the webmasters of these sites have used SEO tactics to ensure top rankings.

The paid (or “sponsored”) listings usually appear on the top, bottom and to the right of the regular organic listings. Usually these are pay per click (PPC) ads, which means the website owner only pays when someone clicks on his ad (as opposed to paying for impressions).

This isn’t an either/or game. Just because you do SEO doesn’t mean you can’t/shouldn’t use PPC and vice versa.

SEO is not free traffic, it takes time and/or money to get good organic rankings but in the long run it’s usually cheaper than PPC.