The site blog lets you add commentary, descriptions of events, and other material related to your site.
Site members can create, edit, and add comments to blog postings. The postings can be saved as drafts and then, when ready, published to the internal blog. Members can also choose to publish posts to an external blogging site (WordPress or TypePad).
Note: See Customizing a site for how to switch the blog on and off for a site.