Normally, Vector objects are created relative to their local coordinate system. The user interface, however, always presents vectors relative to the world coordinate system. Thus, a vector created by evaluating Vector(1,0,0) in a Part whose localFrame is oriented the same as the world coordinate system may be reported as a Vector of 0,1,0.
Frames define coordinate systems. They are essentially transformation matrices from the "world" coordinate frame. Frames can be used to position Parts, but rules regarding frames are ignored when constraint-based positioning is used. This behavior is controlled by the ignorePosition? parameter, which is common to all positionable designs.