Basically the author says most of us have lost the ability to concentrate in this digital era. We are hopping from link to another without really doing anything useful. Our brains love this, its the primitive default and holdover from our legacy as monkeys, however meaningful work takes place through long stretches of intense focus, say you one learning programming or engineering or music etc.
This below summarizes it well
Deep work is the ability to focus without distraction on a cognitively demanding task. It's a skill that allows you to quickly master complicated information and produce better results in less time. Deep work will make you better at what you do and provide the sense of true fulfillment that comes from craftsmanship. In short, deep work is like a super power in our increasingly competitive twenty-first century economy. And yet, most people have lost the ability to go deep-spending their days instead in a frantic blur of e-mail and social media, not even realizing there's a better way.
