
To keep it easy, Two Black holes when combined by a throat or tube is a Wormhole.
Therefore a wormhole means something which has two black holes as two Mouths connected by a tube. For example:
()====()
here () is a Black Hole
===== is the throat
and ()=====() is a Wormhole.
As you know that Black holes attract every object towards it, so to come out of other black hole is impossible. For this concept of White Hole is proposed.
A White hole is a something opposite to a Black hole, it pushes out particles rather than attracting it.
In an Article about UFO travelings:
" They create controlled Blackhole at the entry and a controlled Whitehole at the exit. The UFOs first accelerate to the center of the tunnel using gravity of the Blackhole characteristics and then use the controlled exotic matter phenomenon to get out of the tunnel through the Whitehole. Artificial wormholes simulating Blackholes are needed for space travel and time travel within the physical universe. That is exactly what the alien civilizations use to travel instantaneously through time and space."