Property owners may be liable for accidents on their property depending on why the person is on the property, whether or not they have permission, and if the person was acting in a safe manner.
Trespassers are those who are on the property without permission. The only duty owed to these trespassers is to not purposefully and/or willfully harm them on your own or by setting traps. Child trespassers, however, are not treated the same way with regard to dangerous instrumentalities, like explosives or electric wires that are hidden but are accessible to children.
Licensees are those who have permission to be on the property, such as social guests. Licensees are owed a duty of reasonable care to inform them of potential hazards. Property owners are not required to rid all their property of potential hazards, but only to inform them of known hazards that may be a foreseeable problem to the licensee.
Invitees have a much greater expectation of care from harm. Invitees, such as a customer in a store, are given the greatest duty of reasonable care to prevent any harm from coming to them. Property owners must look for possible hazardous conditions that may befall an unsuspecting invitee. Property owners owe them a greater duty of care because they are invited onto the property for the financial benefit of the property owner.