I might be misremembering it (I think she said it on Twitter), but the way I understand it is as follows.

If you use your computer only through Nautilus, Firefox, and Instagram, you will commonly encounter software problems that you cannot solve, or solve only through a lot of manual drudgery. But, with a deeper understanding of the layers behind the simplified interface—layers which, for historical reasons, commonly work through "command lines", such as the JS console in the browser, the GRUB command line for booting Linux, or of course the Linux bash prompt—you often need only minutes to solve problems that would have taken hours or days to solve by hand.

Similarly, today, if you want to solve hardware problems, you will often find yourself confronted with datasheets or forum threads that are written in Chinese. If you don't speak Chinese, you will either be unable to solve the problem, or you will have to reconstruct the information needed through experimentation, or by help from someone who does speak Chinese.