As one of the first full-scale, AAA virtual reality games, Half-Life: Alyx has to deal with all of the usual difficulties of VR titles, including motion sickness and offering an experience to both seated and mobile gamers with smaller and larger play spaces. That means dealing with locomotion, and potentially offering a few different ways to get around in the virtual world to cater to different player types.
Half-Life: Alyx's solution is to offer three different methods. The first, is teleportation. It would work just as well for those in seated or standing play spaces as it would in a roomscale space. It's comfortable on the brain and the stomach, and though arguably one of the more immersion breaking methods, it's a great starting point for new VR users.
Continuous locomotion is a more traditional movement system based around typical FPS control. It's a little nerve racking for new VR gamers, and can cause more nausea because of the disparity between real world movement and virtual movement. But it's much more immersive.
The final option is Shift locomotion, which is somewhere in between the two. Instead of "blink" teleporting where the player just appears at their new location, Shift zooms them towards it quickly. It's not as immersive as continuous, but it's more comfortable, and keeps you in the game much more than typical teleporting.
You'll be able to try out all these locomotion efforts in Half-Life: Alyx when it launches on March 28, on all commercial VR headsets.