The phrase search engine optimization can be characterized as shaping a website to be more 'search engine friendly'. This method of sculpting or structuring a website is simply giving search engines like Google, Bing, and Yahoo what they require in deciding the position and ranking of a website.
Wikipedia » defines it this way:
"Search engine optimization (SEO) is the process of improving the visibility of a website or a web page in search engines via the "natural" or un-paid ("organic" or "algorithmic") search results.
In general, the earlier (or higher on the page), and more frequently a site appears in the search results list, the more visitors it will receive from the search engines users."
The objective of search engine optimization (SEO) is attaining optimum ranking for your website in ALL the search engines. It all comes down to 'optimizing' your site and it's relevancy, so that when a search engine is calculating its SERPS (search engine results pages), your site will be listed among the 'creme de la creme' of results for your keywords.
There are many things a search engine like Google, Yahoo or Bing actually look at when ranking a website. This includes both on-site factors as well as off-site factors.
Link Building - Other sites that list your site including national and local directories, and sites related to your type of business, which is very critical to Google.
PPC Ad Campaign - Paid for ads like 'pay per click' etc. such as Google AdWords.
Social Networking Sites - Facebook, Twitter, LinkedIn, Google+ etc. Be sure to contribute in a meaningful way, and you will be rewarded.
Social Bookmarking - Digg, Tumblr, StumbleUpon, Reddit etc.
Social Shopping Network - If you are an ecommerce site, you can post to Pinterest etc.
Blogging - Create your own blog or contribute to others.
Video Sharing - Share your video on YouTube, Vimeo, Dailymotion etc.
Photo Sharing - Share your business related photos on Instagram, Flickr, Photobucket etc.
Business Reviews - Ask your customers to review your business on Google, Yelp etc.
Forum Postings - Contribute to forums related to your business.
Articles - Write an article and submit it to other sites related to your business.
Press Release - Write a PR and let the world know about your latest product, business news etc.
Classifieds - Post to classifieds sites like Craigslist.
Document Sharing - Share your documents, brochures etc. with Google Docs etc.
RSS - Let everyone know when you post an update, news item etc.
Off course building your brand by employing the above off-page factors will certainly bring attention to your business. However, the most effective tool to utilize is Google and other search engines like Bing and Yahoo in a concrete way. You can maximize your presence in the search engines by the optimization of your website. After all, what's the use of having a website, if no one can find it? There are a plethora of ways to optimize a website.
The major factors in optimizing a site are titles, meta tags, and web page content.
Titles - Each web page has a title, found at the top of a browser, or listed in the browser tab, not on the actual web page itself.
Meta Tags - The most important meta tag is the description tag, used to describe an individual pages' content. Google will list this description in their search results. Although not used by the major search engines at present, the keywords meta tag can also be utilized. Meta tags are found in the source code of a web page.
Web Page Content - The actual words or text on your website. Not only used to describe your services/products, but also should offer up information. Content should be useful and categorized. Google will love your site if it is offering useful information to your visitors, not just the usual business descriptions etc.
Other On-Site Factors:
There are many other on-site factors to consider. Some of these factors are known, others are assumed.
Keywords in URL - The keywords related to your site being used in a web address.
Image Alt Tags - This tag describes to the search engines (and blind people) what an image or photo is consists of.
Address and Phone - Especially if your business is locally targeted, using your address and phone on every page is good for SEO, and for your visitors to easily find you.
Headlines - H1, H2, H3 etc. These tags denote the important sections of a web page, in descending order. To a search engine this is important.
Internal Linking - Linking to other pages on your site, from your site.
Mobile - All of your web pages should look good not only on desktops and laptops, but on small screens like smart phones, iphones etc. Google will list mobile pages separately, if a person is searching from a smart phone. Make sure your site is mobile friendly.