From BlenderWiki

Object types

You can have several object types. The Object type menu is where you define all properties associated with active objects. Active objects are evaluated by the physics engine and treated as more than simple world objects.

You can choose these object types:

• Occluder
• No collision
• Sensor
• Static
• Dynamic
• Rigid body
• Soft body

Object physics in case of no active World

If you don't have an active World in the Shading Context (Buttons window, F5), instead of the Object type panel you will just see a button named "Physics": enabling it, you will be able to click on more buttons to obtain a panel as in Objects physics with no active world. In this case, the available options are documented here.

In general, you need to create a world because it also sets up a physics environment.