Can you tell me anything about sitemaps and SEO?

[fdrix]

Everybody is talking about sitemaps irrespective of the reasons. What effect does a sitemap has on a website. Is it beneficial for a website to have a sitemap? If sitemaps are useful for websites and makes the process of navigation easier for websites, then I would be eager and happy to get one. I have been planning to launch my website during the recent times and I would very much want the launching process to move smoothly without any impediment. May I know the pros and cons of having a sitemap on a website? If you could provide any suggestions, it would help me a lot.