Obviously, Cubase and Nuendo have a lot in common. Cubase is more tailored for the music production (songs, albums) as it has many virtual instruments that come with it (synths, samples, sample content). But it can of course be used to compose music to picture with tools that help you manage tempo in a way that your musical hit falls exactly onto a scene cut.
Nuendo is more tailored to adding, arranging and mixing sound effects for film and games. I has a special ADR tool that helps you record voice-over at the right places in a movie. With the ADR tool you can jump from line to line and the text is displayed on the monitor for the talent to directly read off of the screen. Or you can batch-export dozens or hundred of sound effects files to a game in one go, something Cubase cannot do. Neither has Cubase an ADR tool.
Stuff like that, of course this list is not complete, it just gives an idea.
I deliberately say “more tailored to” as you can also use Cubase to do sound effects for film. You can create tracks, mix sound effects and so on. But Nuendo just has the broader tools palette that help you with workflow steps usually found in audio post production for film and games. And vice versa.