The easy part of your question is to describe the night light. It probably is a standard bulb (called "incandescent"), with a very hot little wire (called a "filament") in it. The wire is so hot that it emits light. The little particles in the wire that emit the light, the electrons, are moving every which-way, because they're so hot. There's no reason for them to choose one direction or another to emit the light. Bits of it go every possible direction.
Now we get to the hard part- the laser. It works in a rally different way. A collection of, say, argon atoms are prepared in high-energy states. When they fall down to lower energy states they emit the extra energy as light. So far, what I've described is not all that different from the high-energy electrons in the wire. However, there are key differences. The electrons are just plain hot, which means they have a whole range of different energies. The laser atoms are prepared in special states with very narrow ranges of energies. That means that each blip of light that they emit as they fall into their lowest-energy state has almost the same energy. Blips ("photons") with the same energy have the same color.
Ok, so finally here's an answer. Each atom in the laser would, on its own, take a fairly long time (by atom standards) to emit its light. However, the presence of the light from other atoms stimulates the emission of light in exactly the same state as the previous light. (That's a fundamental property of light emission, known since early work of Einstein.) So the new light is going in the same direction as the old light.
BTW the "se" in "lase
r" stands for "stimulated emission", the process we just described.
Now I've given you a reason why the laser light should beam in a single direction. How does the laser set the direction? Some partly reflecting mirrors in the laser allow light traveling along one direction to build up and trigger more light in that direction. Other directions don't build up.
I hope that at least gets you started.
(published on 05/18/11)