In simple terms, Keywords are the words (or search terms) people use to search. It’s what they type into Google or Bing etc.
If you want your website to show up when people search for a specific keyword, that keyword must appear on your site. Competition for certain keywords is very hot and search engine algorithms are increasingly complex, making it much harder to appear in the first few pages for popular keywords.
The most effective ways to use keywords to get traffic from organic search has become something of a craft that forms part of SEO (search engine optimisation) and developing a list of keywords is essential to a successful content strategy. Generally speaking, for SEO, keywords should appear in the page title, the meta description, headlines, anchor text and text but in a natural, readable way.
So, saying something like ‘If you’re looking for sausages in London then London Sausages make the best sausages in all of London.’ is a no-no.
Keywords are also used in Paid Search / PPC advertising where the competition for that keyword will dictate how much it will cost for your to advertise.