Human attention is limited. At any given moment, the brain must select some information for focus and push other information into the background. That filtering function is essential—but it also makes attention vulnerable to distraction, overload, and manipulation.

In a world built to compete for focus, attention has become both a psychological resource and an economic one. To protect attention is, increasingly, to protect the quality of one's life and thought.

Reference:

Wikipedia: Attention

https://en.wikipedia.org/wiki/Attention