I got an idea from the immutability site. It's huge. In pervious Web apps, for example Backbone and Vue, the Model part of an app is simulated with plain JavaScript apps wrapped inside a class. In Redux and in Elm, that's different since we don't embrace mutable states any more. And it changes the Model part a lot.

I'm on the Clojure side, in our words, values are not mutable, however references are mutable. For example, you got a variable for a apple called a, it's two things. There's an apple and a variable called a that is a reference to the apple. When you Joe holds a in his hand, it's merely a reference. As he changes the thing in his hand to a pear, a becomes a pear. An apple never changes into a pear, but the reference changed.

Back to the Model, values in the model does not change themselves. With immutability, we have to create new values and mutate the reference. After the reference it changes, i.e. store is updated, we pass the store to the view to render it. In Clojure, reference is represented in an atom like (atom a). In JavaScript, there's no clear concept like reference, it changes the variable directly. In Elm, it can be more complicated since languages like Elm abstracts mutable states with Monad and it's somehow beyond my knowledge. But the similarity is, you are prevented from mutating Model directly.

And yes there's differences inherited from the languages, Elm, JavaScript are Clojure handles mutable states in different ways. JavaScript is simulating immutable data with mutable objects, it's never easy. I'm not able to explain the details, but you may have already felt that.