OPALS's reason for visiting the ISS is to test our ability to beam video and other information through Earth's atmosphere with lasers. Think of it as a modern-day equivalent to Star Trek's subspace radio. If it's successful, OPALS will be capable of boosting our space-faring communication bandwidth from the current standard of 200 to 400 kilobits per second to a much more respectable 50 megabits per second. To recount the words of the project's systems engineer, Bogdan Oaida: "It's like upgrading from dial-up to DSL."
Opals is aboard today's SpaceX rocket, and so as long as Elon Musk's crew doesn't pull anything crazy, it'll be delivered to the ISS in practically no time. Once aboard and functional, the OPALS laser will locate a ground-based telescope and form a laser communication link. Videos will then be fired through the laser beam, each lasting about 100 seconds while the ISS and ground telescope are in line-of-sight.