I enjoy dhh articles, but find them a bit hard to understand not being a rubyist. dhh says: 2. Server creates or updates a model object. 3. Server generates a

I enjoy dhh articles, but find them a bit hard to understand not being a rubyist. dhh says: 2. Server creates or updates a model object. 3. Server generates a JavaScript response that includes the updated HTML template for the model. Why does a template need to be updated? Isn't that part of the idea of templates, that they are fixed for changes in the model?