When you, as a member of the general public, are invited onto the property of another—whether it's restaurant, a store, or another person's home—then you are legally known as a visitor or invitee. Therefore, the property owner has a duty to make the property safe during your visit. This includes making an inspection of the area to make sure there aren't any dangerous conditions, warning you of conditions that cannot be fixed, and even rescuing you in the event that you are injured because of a dangerous condition on their property.
For example, a restaurant owner is required to make sure that the floor is clear of any spills and that the chairs that people are sitting in are sturdy, that the food is safe to eat, that minors aren't being served alcohol, and that the staff hired is adequately trained to do their job correctly. The owner is also required to warn you of any conditions on the property that can't or haven't been properly fixed, such as a spill on the restaurant floor that still has to dry. Lastly, in the event that you slipped on a spill on the floor, collapsed to the floor due to a faulty chair, or were injured by a negligent staff member, the owner is required to exercise reasonable care to extricate you from the danger and render aid if you are injured.
There are exceptions to this general rule, however, and an invitee is only an invitee within the scope of the permission to enter and use the premises granted by the landowner. For example, if you are invited to a restaurant to eat in the main dining area, and you slip on a spill while snooping around in the kitchen, you are no longer considered an invitee because you have left the boundaries of where the restaurant owner invited you to dine.
There is a special rule in Arizona concerning social hosts and guests of parties that is worth noting. Although bar owners are responsible for not over serving a visibly intoxicated invitee at their bar, social hosts that invite guests to their house for a party are not responsible for an invitee who drinks excessively and then gets into an accident, unless they are a minor.