A word or phrase in the content of your web pages that matches the words and phrases users are entering into search engines as closely as possible. The idea is to speak the same language as users when they make their search queries so you rank higher in their organic search results based on relevance.

Building an Opt-In List, Building Relationships
If you aim for success, you must do everything within your means to achieve that. You just donÃt go on sitting there in your house complaining about not getting as much profit as you expect.