If you don't build a moat, or you didn't build on real estate that already has a moat in place, even the most beautifully designed sand castle will drift away just as soon as a large enough wave reaches its walls. Your kids probably already know this, but do you?

Unfortunately, most companies (even highly successful ones) don't have that kind of defensive characteristic -- that is, they don't have a means to protect themselves from the attacks of competitors. They don't have any moat. But some companies definitely do.

What is a moat and how do you know whether your company has it? Analyst Nick Kapur illustrates the point by describing the difference between two mega-tech companies, Google (Nasdaq: GOOG) and Microsoft (Nasdaq: MSFT), and also explains why you've got to be looking for this crucial characteristic as an investor. Watch the video here:

For more videos, go to FoolTV.com.