What is a Universal Binary?

What does it mean when an Apple site asks me to download a Universal Binary?

Every computer has a certain brand of processor, and computer programs are built with these specific processors in mind. Up until 2005, Apple used Motorola PowerPC processors in their computers. At a developer’s conference in 2005, Steve Jobs announced that era would be coming to an end as Apple moved their architecture to one that made use of Intel processors.

Despite that new Apple computers come loaded with Intel hardware, there are still plenty of people using older machines with the PowerPC architecture. To cater to these customers, Apple makes use of Universal Binaries in distributing applications. Universal Binaries contain the code necessary to run on both Intel and PowerPC processors. By distributing Universal Binaries, Apple avoids the confusion that would undoubtedly arise from distributing two versions of an application and requiring each customer to choose the correct one.