Keywords are one of the most important aspects of copy writing and on-page search engine optimisation. Keywords are single words and short phrases of two or three words that define what a webpage or website is about. They tend to occur with greater frequency on a page than other words, and in more prominent locations such as titles and headings.
In terms of search engine optimisation and internet marketing, keywords are the words and phrases (search queries) that users type into search engines. As a website owner, you want to optimise the keywords used in your page content in order to increase the likelihood that a search engine will return a page from your website in response to a given search query. Ideally, a link to your website will be found on the first page of organic results returned by a search engine.
Well written content (or "copy") balances the needs of human end users, who require relevant, easy to read information, with the needs of search engine which use mathematical algorithms to identify keywords and determine what a webpage is about and how relevant it is to a query. The words used on a webpage, including what type (keywords or stop words), how they are used (alone or within phrases) and where they are used (link text or non-link body text), can all influence the value of the page in search.
Keywords can be broad and generic (head keywords), or they can involve more specific combinations of several words that include a head keyword (long-tail keywords). Generally speaking, it is more difficult to rank on the first page of results for a head keyword because of the number of competing results, whereas more specific long-tail keywords are a better target. For example, "cleaning" is a head keyword used by many thousands of websites, whereas "cleaning Mildura" narrows down the field to cleaners in just one city. A three word long-tail keyword such as "carpet cleaning Mildura" narrows the field down even further.