What is the concept of a time machine? How does it work?

To locate an object in a plane, we require four dimensions — length, breadth, height and time. We all travel frequently in the first three dimensions, but can’t do it in the fourth dimension `time’. Time machine is a device or vehicle that can potentially take us into the future or past and let us stay in that era, just as in fantasy movies. All dimensions have a fixed frame of reference, but we can’t define time. Most scientists believe the ‘Big Bang Theory’ as the origin of time.