Deep work is a term coined by computer science professor Cal Newport, defined as 'professional activities performed in a state of distraction-free concentration that push your cognitive capabilities to their limit'. These efforts create new value, improve skill and are hard to replicate.
Newport contrasts deep work with 'shallow work': non-cognitively demanding, logistical tasks often performed while distracted (most email, routine meetings, administrative tasks). Shallow work is necessary but does not create significant value or develop skill. The central argument: the ability to perform deep work is becoming rarer (due to constant distraction) and simultaneously more valuable (in a knowledge economy).