Don't forget the fully fledged remote desktop thats built in, WebVR (which is being replaced with Web XR), Web Bluetooth, Web USB (aka Web Serial), the API's for notifications, ambient light sensors, an entire transactional database (indexed DB), the language translation API, the Gamepad API (videogame controllers), hardware passkeys (yubikey), speech to text, text-to-speech, webGL, webGPU, webworkers, service workers, an entire suite of cryptography tools, GPS location, battery, vibration, FileSystem API, picture-in-picture API, WebRTC, WebSensors, etc.
And then, on top of all that, building a miniture OS-kernel so that tasks can be sandboxed scheduled/executed and prevent 1 tab from crashing everything or hogging resources.
I didnt upvote the other python-beginer friendly meme cause it wasn't accurate. But this one is on point.