Obviously, search engines such as Google and Yahoo are the main portals for most people into the internet. They come looking for information. To find it, they enter words or phrases or sometimes even complete questions. The job of the search engine is to take those words and return a list of websites that include them. In returning these results, frequently called SERPs (search engine result pages), the search engines attempt to order them by importance. The methods of doing this varies from one search engine to the next and the precise algorithms used remain largely secret.

People will generally make several attempts to find a website that provides the information they seek. Trying different words and combinations, people sift through billions of pages, hopefully to find one or two that fulfils their need.

Why are they important?

If marketers can discover what keywords people use for various searches, they can create pages that (hopefully) are targeted to those keywords. This means marketers can position pages with a carefully designed sales message that appear to people making specific searches. It is a method of targeting sales messages to people who might be in the market for specific types of products. Contrast this to a newspaper or television advertisement. Much more money is required to broadcast the message because it goes out to everyone - not just the small subset of qualified buyers.

Website developers expend a huge amount of effort trying to optimize their sites and pages for certain groups of keywords. The goal for a site owner is for his or her site to appear in the first page of a search. A website link that might appear in the 10th page of a search is highly unlikely to be found (and visited) by most searchers. Among the tens of thousands of competing webpages for any search term, you want yours to be the one that is found. The process of optimizing websites for search engine keywords is called SEO (search engine optimization).