Why does this rescue syntax work?

Ok so i have this method of an application I am working with and it works in production ...My question why does this work. Is this new rails syntax

def edit
   load_elements(current_user) unless current_user.role?(:admin)
 
   respond_to do |format|
     format.json { render :json => @user }   
     format.xml  { render :xml => @user }
     format.html
   end
 
 rescue ActiveRecord::RecordNotFound
   respond_to_not_found(:json, :xml, :html)
 end
 

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