Why Durable Competitive Advantage Matters?

Durable competitive advantage: it sounds nice, but what does it mean? And, as an investor, why should I care about it? Sometimes referred to as a "business moat", durable competitive advantage, in its simplest term, means the scale of a business in its field vs. its peers. That is its "competitive advantage."

But what makes it durable?
What make an advantage durable is the cost and time it would take a current or potential competitor to grow large enough in this area (high barrier of entry) to adversely impact our business. A high level of durability allows us a greater degree of accuracy to predict future earnings, and thereby arrive at a price for which we are willing to purchase a piece of the business (share of stock).

How do we recognize and find those businesses that have this (or don't)?
Strict adherence to the "durable" portion of the phrase enables us to do one thing before we even begin to look at possible stocks: eliminate entire sectors of possible investment. This makes our investing easier by shrinking the field of candidates, while reducing the chances of mistakenly investing our money in a good company in a lousy business.