Lower-power laser systems can be used to send and pick up information. Though they use many of the same ideas and methods, scientists and engineers are somewhat different. Scientists want to know how the universe works. They may see it as an enormous jigsaw puzzle to solve for its own sake. Though they certainly want to help people, their major goal is understanding, not usefulness.
Engineers try to use the facts of science and math to do things that are useful to people.
Quite a few things, actually. Scientists and engineers are important members of our society. Scientists and engineers usually do a variety of things in their jobs and are usually well paid. Math is important, but good reading and writing skills, common sense, curiosity, and general knowledge are also important. Here are some great web links and other resources on optics.