How does a game know you're there?

hey guys 👋
we just finished a new animation, and this one is about something every engine has and almost nobody explains properly: how a game knows you're there.
the short version. your character has a collider, the world has trigger volumes, and when the two overlap the engine fires an event. that's it. that's the whole trick behind every door that opens by itself, every cutscene that starts when you walk into a room, and every trap you wish you hadn't stepped on.
instead of writing that on a slide, we drew it. a knight walks into a pink box, the box lights up, a gate opens. two minutes, no code.
hope you enjoy it, and tell me what you want explained next 🙌