SEO is an acronym for Search Engine Optimisation, which means configuring a website so it is easily indexed (read) by search engines like Google and Bing to display webpages within searches. The objective is to obtain higher organic visits to a website.
SEO extends into many sub-categories from the age of your domain name to the amount of original content on the site. The best place to start is with keywords specific to the websites objective. For example an ecommerce site selling Women’s shoes might anticipate people searching for “buy Women’s shoes” or “Women’s shoes online”. The keywords need to be listed on page and within specific tags, this helps search engines understand what the site is about and therefore listing the web page in its search results when these keywords are entered.
A dated theory to improve organic search engine results was to keyboard bomb a web page. Have you ever seen super small writing at the bottom of a website? This is keyword bombing and has largely been made redundant by updates to search engine crawl algorithms. Attempting this now will at best waste your time or more likely penalise your site by pushing it to the bottom of its index. The industry rule of thumb for keyword content is about 2%. Here is a great tool to check your websites keyword density.