All of the communication platforms have shifted over the years. "Blog" "email list" "site" and others can be kind of confusing.
Some of the differences are semantic, but certain functionalities will differ.
This group where you are posting began as an "email list" - it used to be managed as a "listserv" which was a type of email-only communication. You would email a specific address and everyone subscribed to that "listserv" received the email. That was a precursor to this current "group" format. The difference was that the listerv communications took place only through email. There was no place on the internet you could interact with the conversation threads. (Many listservs were archived online, so you could search the conversations.
The benefit of a listserv was that individuals could be specifically allowed to participate or banned if they misbehaved. This was an attractive, more private option compared to "Usenet" which was a set of public discussion boards and tended to be very "wild west" at times.
Blogs are technically website pages which are published in a way that interested parties can be notified with each new individual update, or "post". Many blogs would provide the ability to comment on each post, so you might carry on conversations with other readers or the author right on the page. In many cases, if you are subscribed to a blog, you will receive an email that contains the full post, which you can read through your email account. Classic blogs have a single or limited number of authors, and the rest of the folks are reading/subscribed to what is published.
Also, there are BBS's or Bulletin Boards which usually required a membership and then would allow a verified user to read, interact, comment on topics or threads. Some of those have a lot of formal structure. Others are very free-wheeling.
This is a "Group" which runs through the Google Group framework. This group requires registration and permission to join. Once you do that, you can choose to receive the "posts" (or as Google Groups now calls them "Conversations") through email only - like the Listserv - or view it on the internet - similar to a BBS.
This is not a "Riv blog site" as no one is specifically posting articles or topics. Anyone is capable of asking questions or providing answers or experiences. It's similar in behavior to a BBS (or more currently a Discord server) in that the content is driven by everyone who participates. Also - this is not directly connected to Rivendell Bicycle Works.
So if someone says the "Riv Blog Site" I would tend to think they are talking about Grant's "Blahg" or the Rivbike News Blog
GP's -
https://www.rivbike.com/blogs/grant-petersens-blogNews Blog -
https://www.rivbike.com/blogs/newsWhere it gets confusing is that someone reading them via email might think of them as "emails" while someone on the RBW Owner's Bunch Google Groups page would think of them as posts.
Hope that helps a bit. There are more details if you are interested.
The Bicycle Lifestyle info is yonder -
https://www.peterwhitecycles.com/bl.php