Eficiency has everything to do with quality. Is a person truly a good worker? Do they perform all tasks in a quick, logical, and professional manner? If the answer is yes, then the person is efficient. Productivity is more focused on quantity. How many car doors did Jim install during the 8 hour workday? How many houses did Nancy sell last month? How many new members have Sam and Lindsey brought to the gym this pay period? Productivity is how much you produce for your company; efficiency is how well you work. Can someone be productive, but not efficient; yes, but they need a help of a manager to become more efficient which will make them more productive as well. Someone who is efficient but not productive works too slowly to fabricate the same amount of work or sales that a "productive" employee does. I hope this helps!

Productivity means that you are doing something that is helpful towards what you are doing. - Ex. I was very productive today. Efficiency means that you are doing something fast and without any extra things that would take away from the fastness. - Ex. I could be more efficient by stopping taking breaks every 45 minutes.

What difference does it make why he is asking?

There are a lot of factories in China, not so many in the US anymore. I can't help but wonder if the reason you're asking this question is because these words are just so much a part of Chinese culture nowadays.

It is a great help! Thank you so much for your thorough explanation.