Why Sitemaps are important?

• A sitemap is navigational tool that lists every accessible page in the site according to the site hierarchy. 
• There are two basic kinds of sitemaps: One that is designed to be read by humans, and the other designed for visiting robots, crawlers and spiders.
• Site should have both kinds of sitemaps, and they should be updated whenever new content or products are added to store.

HTML Sitemaps (for Humans)

The HTML sitemap is like a table of contents. It can be formatted any number of ways.

XML Sitemaps (for Spiders)

• XML sitemaps are designed to extend a helping hand to visiting robots, crawlers and spiders. The sitemap tells search engines how often web pages are updated, the last time each was modified, and the relative priority of each page. 
• The sitemap file (sitemap.xml) is placed at the root (or topmost) directory of site where it can be easily found whenever site is crawled. XML sitemaps are one of the most effective ways to ensure that  site is listed in the major search engines.
• Its companion file robots.txt, contains additional instructions for the visiting robot.

Sitemap Generators

• Although sitemaps can be created manually, it's a whole lot easier to use a program that automates the process. There's a wide range of software available, much of it for free.
• Here's a comprehensive list of sitemap software

1. Google's own Sitemaps Generator.
2. XML-Sitemaps.com is an online service that will generate a sitemap up to 500 pages at no charge and few minutes. When the code is complete, copy and paste it to Notepad, save the file as sitemap.xml, and FTP it up to server. Then make sure to let Google know that updated sitemap and that site is ready to be crawled.
3. PowerMapper  generates a wide range of visual sitemaps -- in addition to the standard text-based HTML and XML.As it scans the site, it captures meta data and generates a thumbnail of each page, and then uses the information to create a map.

A visual sitemap is a great planning tool for anyone who designs or manages a website.

Each map is fully hyperlinked,  drill down and jump to a specific page.