The information is encoded in the beam as variations in the frequency or shape of the light wave. The good part is that since light waves have much higher frequencies they can also hold much more information. Not only is the particle the smallest light unit but it is a particle as well as a wave. Even if the light is of a single frequency that statement would also be true. A laser is useful because it produces light that is not only of essentially a single frequency but also coherent, with the light waves all moving along in unison.
Lasers consist of several components.
A few of the many things that the so-called active medium might consist of are, atoms of a gas, molecules in a liquid, and ions in a crystal. Another component consists of some method of introducing energy into the active medium, such as a flash lamp for example. Another component is the pair of mirrors on either side of the active medium which consists of one that transmits some of the radiation that hits it. If the active component in the laser is a gas laser than each atom is characterized by a set of energy states, or energy levels, of which it may consist. An example of the energy states could be pictured as a unevenly spaced ladder which the higher rungs mean higher states of energy and the lower rungs mean lower states of energy.