A site feed is what allows other people to subscribe to your blog. The technical term is called a "feed aggrigator". Basically it creates a mechanism that pushes your content to other locations every time you make a post. This allows other people to subscribe to multiple feeds which in turn sucks yours and other content provider's content into a single location. Essentially, it allows a person to customize a single web page to view content from multiple websites.
This is one of the big changes you'll notice as the web evolves. Think of Twitter... you create ways for your information to go to your readers/followers instead of them coming to you.
I would like each of you to set up your blogger site to be followed by others. To learn how to do that, go here.