They are part of either a App::PropertyPlacement or App::PropertyRotation. They are vectors but aren't standalone properties and neither App::PropertyDirection nor App::PropertyVector
Axis is the RawAxis normalized upon call
RawAxis is the one you see and set in the property view after expanding the Placement property, but there it's called just Axis
In Python the obj.Placement.Rotation.RawAxis is readonly. but obj.Placement.Rotation.Axis = App.Vector(1,2,3) sets the RawAxis and then obj.Placement.Rotation.Axis will return it as normalized: Vector (0.2672612419124244, 0.5345224838248488, 0.8017837257372732)