This guide refers to snakes that have venom-secreting glands and fangs and whose bite can inflict poisoned wounds. The venom kills the snake's prey and may cause death or serious injury in humans. A bite from one of these snakes should receive immediate medical attention.
in this guide is used to describe snakes that either do not produce venom (they are not poisonous) or that produce a venom so weak that it is no threat to humans. 'Harmless' does not mean the snake will not bite. Snakes do not have feet with claws that they can scratch you with, but they do have needle-sharp teeth and, if threatened, most will readily bite.
The saliva of some snakes slows coagulation so lacerations from their teeth may weep more blood than you might expect. If you are bitten by a harmless snake, you may wish to wash the saliva off and treat the wound with a antiseptic or antibiotic just the way you would the bite of any other animal.