Your blog feed is the Internet equivalent of reading a daily newspaper: readers can subscribe to your feed as they could a newspaper or magazine; they are presented with headlines they can skim in order to get an idea about what they'd like to read, and then link to the post it describes.
Blog feeds are typically in RSS or XML (atom) format, and can be read by "feed readers" or "aggregators", online or offline. Feeds are also used in personalised home pages such as My Yahoo and My Google, offering readers a variety of headlines to browse through each day. Recently, mobile aggregators have been created, so people can also view blog headlines on their mobile phones (I know I do, every day!)
Believe me when I say that you do need to use your blog feed if you have any intention of attracting a readership for your blog. Most blogging software makes your blog feed available for subscription somewhere on the page; you may need to activate this in your blog settings and can also customise the way it looks. For example, you can choose to publish part, all or none of your post content alongside the headline, or even to withdraw your feed altogether (not a good idea!).
Once your blog begins to attract a readership, you may well notice that many of your readers visit your blog's site after first reading your blog feeds. In the near future, I'll be post an article featuring methods you can use to manipulate your blog feed in order to attract a wider audience to your blog. You may even have noticed some of them already!