Actually, in Spain, it is the only compulsory vaccine, and for public health, it is the most important one at a house pet level (we also need to vaccinate cats and ferrets).
A simple yearly dose throughout the animal's life is enough. If we are walking our dog without that vaccine, we can be fined and the liability could be even higher if it bites another person. As you know, this is the most common way of infection.
Rabies are defined as a highly mortal viral disease which attacks the nervous system. It affects all kinds of warm blooded species. It is transmitted through saliva and the most common way to get infected is by being bitten. This syndrome encompasses an increasing paralysis which can be followed by a maniac and aggressive period.
If we want to travel outside our country with our dog, we need to investigate previously about the laws of that country concerning rabies. Some of them require an anti-rabies report which guarantees this vaccine has been administered to your pet. This report can be requested by your veterinary and it is performed by specific labs of the ministry of health.