Kennel cough is a virus easily transmitted with close contact. Vaccinated animals are protected, or at least the symptoms will be much less severe. Kennels, grooming shops or even the park where dogs interact. If an animal is not Vaccinated, this virus can get chronic. Symptom will show up in about 10 days with hacking and coughing.
kennel cough is bronchitis that can be contracted from other dogs, stresses, or bad tempurature, as well as most things that would "cause" a cold in humans. It resembles a chest cold in people. It sounds like something is caught in the dog's throat. The vaccine is the bordetella shot. It can heal on its own, or can be kncocked out by antibiotics.
frosty girl has it right. you find alot of shelter pets have kennel cough from being in close quarters with all the other animals. Some amoxicillian and the bordatella vaccine and they will be up and ready to go in no time. I do the bordatella every year, since my dog goes to work with me (vet office) she is around pets all the time. Its just good to do, they need it for boarding, grooming or obedience classes anyhow, so just do it with the yearly vaccines.