By providing a RSS Feed for your blog you let people keep up to date. Everytime you post to your blog the feed is updated. Alowing users to read your blog from their favorite RSS Aggregator.
Most if not all Blog software provides some sort of feed, automaticaly updating when you publish your post. Users can subscribe to your feed if you provide a link to the RSS feed. Usually a link in the sidebar with the RSS icon next to it. Also browsers now provide the ability to find and subscribe to RSS Feeds. You will see the orange feed icon in the address bar on sites that provie Rss Feeds.
I use FeedBurner to re publish my RSS Feeds. You can see in this page the many benefits of doing so.
Also you can provide your readers to subscribe by email. Allowing them to get daily or weekly updates to your blog.
