Companion is one of 14 trophies that the player can earn in the game, Journey. It is a silver trophy, and is worth 30 points.
To redeem this trophy, you must complete a full journey, (or the majority of a journey) with the same companion.
"Finish the game with the same partner for the majority of the journey and return to the beginning."
This trophy is very easy to obtain, ignoring the possibilities a companion could quit mid-game. Finding a Companion in either the Bridge or Desert levels and remaining with them for the rest of the journey will gain the trophy for you.