You might be surprised how little the world of Web workers actually know about sitemaps. If you've spent any time at all within the SEO community of course the term "sitemap' won't make you blink as you're likely already very familiar. But for the rest, a little education is in order to make use of this powerful mechanism to get pages indexed by the search engines.
A sitemap (specifically a search engine sitemap as opposed to a sitemap built for users) is a file that contains a list of website page URL's that is made accessible by the website owner for search engine crawlers to access and index. Sitemaps are more than just a list of URL's though, they contain important metadata (an additional information layer) about each URL including the time it was last modified, how frequently it changes and the URL's importance in relation to other URL's. Sitemaps are useful for those sites whose pages are not always easily discoverable by search engines or which have trouble getting indexed.
While it is possible to hand code a sitemap, that process can be complex and cumbersome. Fortunately, most modern content management systems (CMS) recognize the important of search engine sitemaps and readily provide the necessary XML files that you can use (see the next step on submission of sitemaps). Check with your existing CMS provider to see what resources they provide. Realize however if you opt to go it alone, choosing to follow the official sitemaps protocol instead, that there are different kinds of sitemaps including those for video, images, news, and even mobile. Each type of sitemap has its own rules so knowing the differences between each will prove of great importance.
Creating a sitemaps is only the first step; you'll also need to submit the sitemap to search engines. Google and Bing both provide platforms (Google Webmaster Tools and Bing Webmaster Tools) which provide a way not only to submit, but track the performance of your website and how it is performing in the search results.
Sample sitemap: