A "blog" is short for "web log." It is a regularly updated journal or diary or report that is available via the Internet to a public audience. For example, "The Way of Improvement Leads Home" is a blog.
A "blog post" is an entry--one entry--on a particular blog. For example, the entry you are reading right now--"What Is The Difference Between a 'Blog' and a 'Blog Post?'" is a blog post published on the blog "The Way of Improvement Leads Home." In other words "What is the Difference..." IS NOT A BLOG, it is a BLOG POST.
Too often people who are writing a "blog post" say, via Facebook, Twitter, or some other form of social media, that they have written a "blog" or a "new blog" when what they really mean is that they have written a "blog post."
- If you have started a blog and you want people to read it, you should send out a Facebook message or tweet that goes something like this: "I just started a new blog called XXX, come check it out at "www.blogaddress.com." I will be doing a new post every day."
- If you have written a new entry on www.blogaddress.com and you want people to read it, you should send out a Facebook message or tweet that goes something like this: "Check out my latest post (or blog post) at www.blogaddress.com.
- This is correct: "Come read my most recent post at The Way of Improvement Leads Home on the difference between a blog and a blog post."
- This is incorrect: "Come read my new blog on the difference between a blog and a blog post.
I am not the only one who seems to be bothered by the improper use of the term "blog." Check out Forrest Wickman's post on the subject at Slate. (As opposed to Forrest Wickman's blog about the subject at Slate).