Okay, picture this, you are writing tons of articles every month and ultimately end up having so many articles in your blog that it’s difficult to put links to each of them at one place so that the search engine can crawl them even after you update anything.
Now, there are 2 methods by which search engines makes sure that it crawls every page of your website -
Through backlinks
There must be some or other way by which search engine can indirectly find the path to your older articles crawling tons of data on your website. It could be either from your website or backlinks from several other websites.
But this is very slow process and your updated content may not show up in search results for long.
You also can’t explicitly tell search engine about the disconnected links that you want it to index.
Sitemaps
Sitemaps comes very handy for search engines letting them know which pages you want it to index and at what duration and priority. Check the standards given by sitemaps.org
For instance, if you have updated something on your blog that was written around a year back, you can mention in your sitemap that this content should be indexed on monthly or weekly basis and so on.
Sitemap is generally a simple XML file which you can write manually or use several of the tools available to generate them.
Wordpress users (self-hosted) should install Google sitemap generator plugin (follow the installation instructions in readme) and add a new sitemap in their Google Webmaster’s Tools as show below -
Not just Google, almost every other search engine checks the standard sitemaps while crawling.
I´m a wordpress.com user. How I add a sitemap in google webmaster?
@Luís de Melo
You just need to verify your blog to Google Webmaster. Once verification is done, your site will be added to your account. And since wordpress.com users have sitemaps already there ([yoursite]/sitemap.xml) you can easily associate it with your added site.
Let me know if you still have any problems. I’d be glad to help you out.