Content is extremely valuable for Search Engine Optimization. While you should still focus on optimizing your sites infrastructure and following other SEO best practices, content is one of the most valuable things you can do for your SEO efforts. Why is that, it's really pretty simple, search engines search content and your site visitors view site content. If a user does a query for a particular topic, it is the job of the search engine to find the most relevant and informative information about that topic and place it at the top of the search engine results page.
For example; You are to do a research paper so you go to the library and begin your research. You pick books that are the most relevant and that have the most information about that topic. Other books that are not as relevant and have very little information about your topic you set aside, or don't even pick up. Then you sit down and explore each book to find the exact information you need. Once you find it, you jot down that information to show it on your research paper.
Searching in the internet works much the same way and the search engines want to make sure they deliver you to websites with relevant on topic content that will satisfy your research needs. Other sites that are not as relevant and have very little information about the topic you're searching for will end up lower on the search results page or even worse yet on a higher search results page. Statistically if your at the top of the search results, more users will click through to your site based on that topic.
Long tail keywords are main search keywords with additional text around the keyword. Obviously more content means more chances for relevant long tail keyword traffic, that your additional content can contain. Long tail keywords have a lower demand and are much easier to improve your SEO rank for. It is better to concentrate on these long tail keywords than to obsess trying to rank for the most popular ones that may take you months or years to improve your rank for because they are locked up by competitors. As your site becomes more authoritative with more valuable content, and becomes more popular because users are finding your site with long tail keywords, your site will naturally move up in rankings.
Chances are you have content you have never placed on your website. This content can be extremely valuable for SEO purposes. Do you have newsletters you send to your clients? These can be a great resource for information that could easily be added your website. What about print media publication or services manuals? Unique content for you products such as specification data sheets or product paramaters. Any information that you present to a client should be in content form on your website. When your done there, run search for your products and services, what content do your competitors have.
In addition to search engines, your visitors will discover your content and if it's good, well written and informative, they will be more likely to use your product or service.
When creating content, don't just copy what someone else has on their website, first off it 's a violation of copyright laws. Second reason is that search engines like Google can detect duplicate content and they may believe you are using black hat SEO practices and not show you in search results pages.