Screenwriting means writing for anything with a Screen
Lately, I've been advising screenwriters to look beyond traditional movies as their platform for storytelling. You should be able to imagine writing for TV, for transmedia, for games, for e-books, web-comics, for websisodes. Your work will appear on computer screens, on tablets, on smartphones, on HDTV, and yes maybe even in the old fashioned, nostalgia-filled movie theater.
The "screen" in screenwriting means anything with a screen.
With that in mind, you should read these recent articles: