The Lab was one of the first big showcases of modern virtual reality, and one of the first experiences many had after picking up a first-generation Oculus or HTC headset. Today, Valve are keeping up with the times and updating their free VR playground to better reflect modern technology, such as their own Index VR hardware.
In what they're calling the Hands-On update, every part of The Lab now gives you properly physics-driven virtual hands, whether you have a finger-tracking controller like the Index or not. They reckon that your skeletal three-dimensional meathooks should be future-proofed and ready to map to controllers that don't exist yet, but also will work with older setups with binary grips or just simple buttons.
And what's the point having hands if you can't poke things and laugh when they fall over? The other major change to The Lab is a physics overhaul. Almost every interactive object is now a solid physics-driven entity that you can pick up, throw, smash or otherwise make a big mess with. Suddenly I understand why cats push everything they can off tables; it's shockingly cathartic.
Under the hood, Valve are making some nice technical improvements that shouldn't be too obvious unless you're looking for them. The Lab should now support all possible refresh rates (such as the Index's 144hz mode) without the physics getting squirrely. They've also made some changes to the audio engine, so that you should have properly spatialized 3D sound no matter your headphones.