SEO is search engine optimization which means your website is friendly to the search engines so the link will be included when someone does a search that is related to your site. For example your site is about tour packages. When someone searches for that item the search engine would present a search list. When your site is SEO compliant then it can even be the first on the list. There are many ways to do SEO on the site and one is the regular uploading of new contents.