Here is an overview of the collection, via Valve:
Including Portal and Portal 2, the Companion Collection comes to Nintendo Switch with all the groundbreaking gameplay, dark humor, and exploration that earned the series hundreds of awards.
In Portal, you’ll use a highly experimental portal device to solve physical puzzles and challenges. Maneuver objects—and yourself—through space to puzzle your way through the mysterious Aperture Science Laboratories.
Return to Aperture Laboratories in Portal 2 where you’ll once again face off with the lethally inventive, power-mad A.I. named GLaDOS. Meet an expanded cast of characters as you think your way through dangerous, never-before-seen areas of the laboratories and a wider variety of portal puzzles. Plus Portal 2 also includes a co-operative game mode with local, split-screen, and online multiplayer so you and a friend can think with portals.
Watch the launch trailer below.