What's the meaning of "do something for nothing"?

What's the meaning of "do something for nothing"?
What's the meaning of "do something for nothing"?

What's the meaning of "do something for nothing"?
It is means somebody do a invaluable and unnecessary things!

忙来忙去，一无所获

do something for nothing做一些无关紧要的事情。

忙碌而一无所获 例如 You can't get something for nothing. 人不能不劳而获。

一无所获

应该是说不计报酬地作些事情
比方：
I like my job so much that I will do it for nothing!

"不劳而获"