硕士研究生和博士研究生和博士后研究生有什么区别？

这是一个学历地位的提高。
研究生一般就是指硕士研究生和博士研究生，好像还没有听说过博士后研究生的。（不过可能是我孤陋寡闻了）

硕士研究生生由大学生经过考试选拔过来。博士研究生由硕士研究生经过考试选拔过来。博士后是博士继续深造而过来的。

一般来说，硕士生还需要导师带领才能完成课题研究，博士生就可以自己独立完成理论课题研究了。博士后吗……不好说了，这个我也不是很了解了。

传热传质系研究生为你解答，供参考。

Let me toss in my 2 cents, though my experience is very North American.

Undergraduates refer to students at university, working towards their first or bachelor degree.

Upon graduation, these students can go into graduate schools. Their are 2 major types: course work and research work. Course work degrees include MBA, MSW, MA, MSc and others. They are like undergraduates courses but the focus is more on advanced skills career training. They are not "real" graduate programs, in a strict sense.

The second type is research programs including Master of Philosophy and Doctor of Philosophy, i.e. MPhil and PhD. The difference between them is MPhil is to verify validity and reliability of existing theo