Search Engine Optimisation (SEO) is a suite of tools that improve a website's visability in a search engine's search results, with the aim being to get the subject webpage or website a higher position in the rankings; preferably onto the first page. This is an organic process rather than paying to have the site featured on the first page. So what is SEO? At its most simple it is a marketing strategy, but one aimed specifically at the internet. It will target many different types of searches including images, videos, plain text, local searched, news and searches on specific industry-specific engines. Optimising a website for searches will involve looking at how users search for the terms and products associated with the site, as well as editing and updating content, amending HTML coding and promoting a site to improve the number of inbound and backlinks. A search engine is a software application that looks for information across the world wide web. This information is collected and collated, indexed and ranked by the search engine. Pages are retrieved for the search engine by a web crawler or spider which is an automated program that follows all of the links on a web page. Information in the titles of the page, the content and in the site code are used by the search engine as part of its classification of a page. All this information is stored in a large database in different formats depending on the search engine being used. When a user types a search phrase (which can be as simple as one word) into a search engine, the engine refers to its database index and returns all the pages that meet the criteria along with a summary containing the title and parts of the text which were collected by the web crawlers. Relevance is a critical factor in a search engine returning query results. While there may be millions of pages containing the searched for text, the search engine has to return only relevant pages for the user. Relevance is determined by the rank assigned to a web page, with pages of the highest rank being returned first. When you look at a web page, you are viewing it at many different levels. You understand the language, you recognise the images, there is a social and cultural context which helps you understand the page. While search engines and their algorithms have evolved dramatically in the past few years, they are not humans and they do not have the human ability to look at a page and instantly isolate elements and meaning. This is why SEO is important, it acts as an intermediary between the human and the search engine and it explains the web page to the search engine so that it can be indexed and ranked properly. This is particularly true today when images, still and moving, social tags and a host of other tools are used in web pages. A search engine does not understand a photograph or video implicitly like a human would, it has to be told what the image contains and what the video is explaining. SEO ensures that all the elements on a website are explained in this way and makes the page not just easier for the search engine to understand, but for the human, ultimately, to read and access.