那是什么和 那个是什么 意思上没有区别,只是断句不同。(那是)什么,(那个是)什么。(那个是)需要说的快一点而已。
"那是什么" is the same with "那个是什么" . The different is you need to speak faster when you say"那个是什么", "那个是" should pronounce as one word. If you choose to say "那是什么", you can speak a little slower just make "那是" as one word.