任何人都可以在 Rails 控制器中解释params：它们来自哪里，它们引用了什么？

  def create
    @vote = Vote.new(params[:vote])
    item = params[:vote][:item_id]
    uid = params[:vote][:user_id]
    @extant = Vote.find(:last, :conditions => ["item_id = ? AND user_id = ?", item, uid])
    last_vote_time = @extant.created_at unless @extant.blank?
    curr_time = Time.now
  end

我希望能够逐行阅读此代码并了解发生了什么。