The only difference between dog urine and human urine is that they come out of differing species. Otherwise, it's next to impossible to tell them apart, unless you have the urine chemically analyzed. Like human urine, dog urine is most concentrated in the morning and then is mostly water later later on. Also, dogs usually do not urinate as much as humans.
Who Did This?
Dog urine contains water, bacteria, ammonia, uric acid and dog hormones. It's these hormones that are different from human urine. Any dog nose can smell these hormones to know the sex, health and even the breed of the dog that urinated. When the dog urine dries, it does so in tiny crystals that can release their smelly messages when they are moistened again from humidity or being sniffed through a dog's wet nose.
Watering the Lawn
The big misconception about dog urine is that it destroys lawns. It doesn't. Dog urine is mostly water and studies have shown that, over time, lawns with dogs in them do just as well as lawns without dogs.