In FreeCAD, Placement defines an object's position and rotation. The Placement concept is explained in detail here: Placement.
Example of setting a document object's Placement:
myObj = FreeCAD.ActiveDocument.ActiveObject
pl = FreeCAD.Placement()
pl.move(FreeCAD.Vector(2,0,0))
myObj.Placement = pl
Description: Constructs a placement, empty or with the given arguments, or as a copy of the given placement.
Description: applies the Placement to the given vector
Returns: the resulting vector.
Description: multiplies this placement with another one
Returns: the resulting placement.