So, here's what we know from this trailer:
The system is called the Switch.
It consists of four main components, being a small screen, two removable controllers and a dock to plug the system into the TV.
The mini screen has fold-out legs to hold it up on it's own.
You can plug the controllers into the sides of the mini screen, plug them into their own sliding dock for use as a traditional controller, or hold each one independently.
The two mini controllers can be used as just that, two separate player's controllers.
A WiiU Pro Controller-like accessory exists for the system.
Skyrim was shown.
A new Mario game, or at least prototype, was shown.
Either Splatoon, a Splatoon sequel, or both were shown.
Either Mario Kart 9 or Mario Kart 8 with more stuff in it was shown.
Some sort of basketball game was shown.
Good stuff m8