A whip (the common name for what we call a bullwhip) is an exotic, one-handed melee reach weapon that only does non-lethal damage.
The whip is a long, flexible, braided leather cord which tapers gradually from the handle to the tip. The handle is either thick braided leather or leather-covered wood and is 8 to 12 in (20.3 to 30.5 cm) long. When stretched to full length, the whip can be up to 20 ft (6.1 m) long. An optional tassel of horsehair or twine on the end (called a cracker) will amplify the sound of the whip. An average whip costs 1 gp and weighs 2 lb (0.9 kg).
The whip can only damage creatures not wearing armor or without tough natural armor. It is a melee weapon with reach, giving it an effective range of 15 ft (4.6 m). Unlike other reach weapons, it can be used to attack adjacent opponents as well. Whips also can be used to trip an opponent and they are particularly good at disarming. However, it takes special training and practice to use a whip effectively without hurting yourself, therefore it is considered an exotic weapon.