Keyword

Computer users find your website or discover your content by typing in keywords on a search engine. The search engine then accesses a list of indexed web pages that contain that keyword. Most search engines won't include you on a search engine result page for a keyword you haven't used on that page, even if it’s a related word to other keywords on your web page or if you've included it in the list of keywords in the HTML Keyword Metatag. Unfortunately, most search engines ignore the Keyword Metatag, so including a popular keyword there isn't likely to help much as far as SEO is concerned.

Most search engines recognize keywords as a computer, not as a human would. This means that most search engines don't link synonyms together (such as "couch" and "sofa"). If someone types in "couch" into a search engine search box, and your furniture website only sells "sofas" and "love seats" you won't show up on the search engine results page. Many search engines won't even list your web page in the search results if someone types in the singular or plural form of a word you do have on your webpage (so if someone typed in "recipes cheese soups" and a web page contains only "Cheese Soup Recipe" it may not show up).

Keywords can be a single word (sofa) or a keyword phrase, which is a descriptive group of words (black leather sofa on sale). There has been a lot of debate over whether one should use top performing keywords only or specific keyword phrases. 

You can get keyword ideas from Google AdWords Keyword tool. Type in a keyword or keyword phrase and Google will give you a list of suggested keywords, along with the statistics of how many people are searching for that keyword every month, last month, etc. It will show the top keyword phrases that are related to your keyword.