Definition - What does Second Screen mean?
A second screen is also known as a companion device.
Techopedia explains Second Screen
A second screen allows for viewer interaction. For example, some of these secondary displays could enable real-time chat about visual broadcasts, such as news or current event broadcasts. Second screens also can help shape how businesses reach customers, and how consumers use state-of-the-art technologies in an increasingly digital world.
The use of second-screen broadcasts also coexists with the emergence of portable data delivery through cloud-based software systems, along with other ways of getting content over wireless platforms directly to a customer’s device.