In what way is Ruby on Rails NOT multithreaded?

Ruby Questions
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1

Disclaimer: I’m a c# ASP.NET developer learning “RoR”. Sorry if this question doesn’t “get” RoR, any corrections greatly appreciated!
What is multithreading

My understanding of “multithread” ability in web apps is twofold:

Every time a web/app server receives a request it can assign a thread to the new request, thus multiple requests can run concurrently.
The app runtime + language allows for multiple threads to be used WITHIN a single request (in ASP.NET via "Async" methods and keywords for example).

In this way, IIS7 + ASP.NET can do points 1 AND 2.
I’m confused about RoR

I’ve read these two articles and they have left me confused:

Clearing up some things about LinkedIn mobile’s move from Rails to node.js
How to deploy a multi-threaded [rubyonrails](http://rubyonrails.org/)

question one.

I think I understand that RoR doesn’t lend itself very well to point number 2 above, that is, having multiple threads within the same request, have I got that right?
question two.

Just to be crystal clear, RoR app/web servers can also do point number 1 above right (that is, multiple requests can run concurrently)? is that not always the case with RoR?

2

I’m no expert on threading.

Rails’ entry point is the router (config/router.rb) which uses Rake for all incoming requests. As for the server being multi-threaded. Rails gets run via one of several server (layers) such as WEBrick, Unicorn, or Puma. Puma is the muli-threading solution that is recommended. The others aren’t so much which means you’d have to spin up extra server instances.

Typically Rails runs as one instance itself. The internal threading I’m not sure about.