We do need government. We need a government that protects our property and our persons from harm by others. In addition government should provide a court system for peacefully settling civil disputes. To accomplish this the use of force is sometimes necessary but it should be very strictly limited. When government goes beyond these limited roles Libertarians believe government exceeds its moral authority and its practical capabilities.
Libertarians advocate a free marketplace for services, goods, thought and speech.
The other three parties advocate force to restrict or subsidize thought, speech, services and trade in goods. Libertarians believe that if there is a charitable need people will voluntarily serve that need at an appropriate level. The other three parties believe that people should be forced to serve charitable needs at the level they think appropriate. The difference is the Libertarian Party does not advocate force to solve every problem. The others do.