Keywords used to be king in internet indexing. The major search engines such as Google, Yahoo Search and Bing used them to index websites in the databases. The more keywords your website had, the more often it would come up in searches. This led to "keyword stuffing". This refers to the practice of writing articles and web content that had the main objective of using keywords as many times as possible. Some website content became awkward and in worst case scenarios website content and articles were totally irrelevant to what the website was about.
As search engines became more refined, keyword stuffing was penalized and sites that used this method began to find themselves ending up either on the bottom of search results or missing out entirely. Recently search engines have developed programs that read websites similar to how a human would read them, from top to bottom and from first page to last page. This means these programs, called spiders, are looking for relevant content and working links to relevant pages and related sites. These spiders also flag duplicate content on websites and reward the site that the content is lifted from. The plagiarized content is penalized in their databases. This means that if you copy and paste content from a site, your site will be ranked lower or not at all. Even if you use the same content on your own various sites and pages, it may be flagged as duplicate.
Now when you are writing your website content or articles for the web, search terms are more heavily rewarded than keywords. What is the difference? Search terms are the phrases and words that people use to search for your site. For example if you own a beauty salon in Tampa and have a website, your potential visitors and clients may search with phrases like "haircuts in Tampa", "best color expert", "hairstylists in Tampa" and similar phrases. When you are considering your website content or articles think about how the site will be searched for and what phrases will be used.
Keywords are still important, but search terms now trump them. Remember to keep your content and articles sounding natural. If you do this, the keywords and search terms will fall into place. Good quality original content beats out anything on your site except working links for SEO quality. Remember, if it sounds unnatural to you, it will sound unnatural to the search engines, too.