Keywords & phrases

Keywords are viewed like puzzle pieces by a search engine. They give search engines a picture of what your site is about. The more relevant keywords the better. Used in appropriate amounts keywords give search engines the bigger picture.

Keyword Density

A measure of the amount of times a unique key phrase appears as a
percentage of the total number of keywords used on that page.
There is no magic number but 10% is recommended.
Sometimes a keyword appears naturally on a page many times this is not a problem as search engines like Google give keyword density less importance.

Keyword Proximity

SE’s place importance on the proximity of keywords to each other.
Many search queries are more than one word which become key phrase searches. The closer together these words are the more importance is given to that web page. If the Key phrase itself is targeted then that will become more important than a page with the same separate keywords but apart.

Keyword Longtails

Longtails describe phrases where the additions of words allow it to become more searchable. the shorter the keyphrase the harder it is to get results. Some keyphrases dont work when shortened as the word is too common and covers.