Submitting sitemaps can be an important part of optimizing websites. Sitemaps enable search engines to discover all pages on a site and to download them quickly when they change. This blog post explains which fields in sitemaps are important, when to use XML sitemaps and RSS/Atom feeds, and how to optimize them for Google.
Sitemaps and feeds
Sitemaps can be in XML sitemap, RSS, or Atom formats. The important difference between these formats is that XML sitemaps describe the whole set of URLs within a site, while RSS/Atom feeds describe recent changes. This has important implications:
- XML sitemaps are usually large; RSS/Atom feeds are small, containing only the most recent updates to your site.
- XML sitemaps are downloaded less frequently than RSS/Atom feeds.
For optimal crawling, we recommend using both XML sitemaps and RSS/Atom feeds. XML sitemaps will give Google information about all of the pages on your site. RSS/Atom feeds will provide all updates on your site, helping Google to keep your content fresher in its index. Note that submitting sitemaps or feeds does not guarantee the indexing of those URLs.
Source ul : http://googlewebmastercentral.blogspot.in/2014/10/best-practices-for-xml-sitemaps-rssatom.html