I have understood that an subscriber, signs up via the wordpress form for get email updates whenever a new blog post is published.
(Of course there is the mechanism for editing, which posts changes every single time a change is published, but I never use it.)

Also if a blog has 10,000 followers within lst 3 months of publishing their blog, I honestly wonder how the person legitimately got it..without furiously liking or commenting on other blogs. (Frankly when I saw that this same blogger 'Liked' a post of mine, it annoyed ne. She was just self-promoting to get more guest blog writers and not caring to establish any civil long term virtual blogger sharing.) I wish I could remove her like. (Yes, awful of me. But that's how I feel.)