He’s Gabe Newell, the founder (and I think still CEO) of Valve Software.
Former Microsoft employee that started up a small game studio in the 90s. They took the Quake engine, modified the balls off of it, and used it to make Half Life, an FPS game that revolutionized the landscape forever with things like real time in-engine cutscenes that wove the story in through the gameplay, and through how advanced the enemy AI seemed. It also featured a ton of miniscule details requiring some clever coding to pull off, which really added to the atmosphere.
They also made the Steam gaming client, Portal, Left 4 Dead, Team Fortress, Counter Strike, Dota 2.
He’s not involved with the day to day much anymore. Pretty much retired in (I think) New Zealand now.
Very nice guy by most accounts. Was still responding to fan emails semi-regularly around 2010, and was one of the main voices in the dev commentary features in their games up through the Orange Box (Half Life 2 Ep 2, L4D, Portal, TF2).