The basic purpose behind the creation of the internet was to provide people easy access to information. Search engines allow you to access that information in milliseconds with literally 1000s of resources. A list is provided, which as you know, ranks the results by what is considered the most relevant resource based upon the terms you entered.
With search engines looking for informational sites, how do you market your company through your website? Your site was created for one goal—to sell your company with the strongest selling terms your marketing experts could create. Now, it needs to provide useful, relevant, and current information or you may not show up in the search results.
When you search for information on the internet, you will see a list of possible answers with certain words called out in bold. People usually do not use complete sentences in queries. Instead, they use individual keywords and long-tailed keywords which are phrases of 3-7 word.
Since these words are just thoughts, it is difficult to put the long-tailed keywords on your site and be coherent to your viewer. That is where the hidden words or phrases come in. You or your website developer can add these search terms into the code where the search engine robots can see them to catalog or index the many parts of your site. When there is a search, the results should show these words.
If you are unclear on how to set these up, speak to an search engine expert. You do not want too many words or too much repetition. As a final cautionary note, do not put in words that do not describe your site. Google and Bing could penalize you for that strategy. If a searcher lands on your site, realizes they have been had and leave immediately, this abandonment, could possibly affect your SEO rankings.