You noclipped out of reality into Level 0. Your friends are in here too. So is something else.
Moving (VR): there's no joystick walking. Push the floor and walls with your hands to move, like a gorilla. Swing your arms and let go to fling yourself. Climb walls by pushing into them. Right stick snap-turns, left Y button mutes your mic.
Rooms: type a code here or on the computer terminal in the starting room. Everyone with the same code ends up in the same room on the same randomly built map. Send your friends the code.
Infection tag: with 2+ players, one person turns into the Entity (black fur, glowing grin). Anyone the Entity touches becomes an Entity too. When everyone's caught, a new round starts. Entities move a bit faster.
Desktop: WASD to move, mouse to look, Space to jump, left/right click to punch (tag people, press terminal keys), T to chat, V to mute, Esc for this menu.
Levels: Level 0 is the hub: the terminal, the vending machine and a safe room. There are 33 more levels behind glowing EXIT doors, from the Garage and the Poolrooms to the Hotel, the Grid, the Attic and the Blackout. Every level goes on forever and is built around you as you explore, so it's different every game.
Monsters: every level has its own monster with its own trick. Some only move when you don't look, some hunt by sound (your voice too), some hide in the floor, the ceiling or the water, and one pretends to be an exit. Most can't climb, so get up high. If one gets you, you're usually sent back to the hub.
Camera & shop: your right hand holds a camera. Pull the right trigger (E on desktop) to photograph entities for points, then spend them at the vending machine: flashlight (left trigger / F), entity detector, exit compass, radio (hold left grip / R to talk to everyone), almond water (B / Q), and security cameras: place one with A (C on desktop), then watch every camera on the monitor next to the terminal. Every new entity you photograph gets filed in the entity index, the computer by the start room's west wall, with your photo and how to survive it.
Staying safe: the player board next to the terminal has MUTE and REPORT buttons for every player. Reporting someone sends it to the developer and blocks them for you. Text chat: press CHAT on the terminal keyboard (or T on a PC), type, then ENTER. Everyone in the room sees it, swear words are starred out, and you won't see messages from anyone you've muted or blocked.