Blogs: Blogs, or more accurately called "Blog Series'", is a series of themed blog entries. An example would be "Game Review Madness", in which you would post game reviews.
Entries: Blog entries are the articles you post to your blog series. An example would be "Minecraft Review", which you could post in the "Game Review Madness" blog.
Subscribing to a blog (series) will notify you every time there is a new entry posted.