UPDATE: A revised and extended discussion of this concept was posted on December 28, 2016.
Important: Strongly affecting the course of events or the nature of things.
Urgent: Compelling immediate action or attention.
What's important isn't necessarily urgent...and what's urgent isn't necessarily important. We all have plenty of urgent matters we're compelled to deal with, despite the fact that they don't really have much bearing on the course of events. But what about those truly important matters that go neglected because they don't compel our immediate attention?
The distinction between importance and urgency seems obvious, but I didn't put it in such stark terms until I took a class in grad school with Joel Peterson, a business heavyweight who's been lecturing at Stanford since 1992. The subject of the class was real estate, but Peterson's final lecture was sort of a free-floating life lesson--a summary of his accumulated wisdom. I refer back to my notes from that lecture on a regular basis and one of the concepts that stands out is this distinction between what's important and what's urgent. (Here's a larger version of the graph above, and here's a one-page PowerPoint, 70 KB.)
I find it a helpful reminder to spend less time and attention on all the urgent crap that isn't truly important, and to devote more to the truly important things that nevertheless lack urgency. (Awareness may not be sufficient--but it's a start.)