Can you explain the concept of Quality of Service?

Put simply, Quality of Service (QoS) is a concept that puts forth the idea that the functionality of a given technology can be measured and improved upon. In networking, this means down time and error rates, among other things, can be accurately deciphered and ultimately reduced to an acceptable level. You can access a full, in-depth definition of QoS here, as well as related product and vendor information here.