What's the Difference Between Google's “following” a Blog vs Subscribe?
If you are using Google's services, you can “follow” a blog published on google's blogger. When you follow, that means, if the blog has a “follow widget”, you will show up there. (similar to Twitter's “followers”.) Follow also means that you are automatically subscribed to the blog, from your Google Reader.
Here's Google Help on the topic: Source.
Not that the “follow” is exclusively a Google thing. Blogs not hosted by Google doesn't have that concept. Google Reader also lets you “like” any particular blog article. “Like” is something like a “up vote” in many websites. Author can also see how many times a particular article has been “liked”, if they are using Google's service.