Blogs offer fresh, unique content. Search engines tend to like that, regardless of the format. If they know any given site is adding new articles on a frequent basis, they will visit more often to index it. Blogs are certainly one way of easily adding new information to your site. Newsletters archived on your site can also provide a similar benefit, as can archived press releases, or a forum.
What is a blog?
A blog is a special kind of website that allows you to regularly update the contents, allows your friends or customers to make comments, and gives you a convenient place to post photos.
How does it work?
A special piece of software runs on the server that holds all of the blog posts and pages, this software gives you a special interface to the blog that lets you make pages or posts easily.