From a coffee pot to video calls
In 1991, scientists in Cambridge pointed a camera at a coffee pot so they could check from their computers whether the coffee was ready. We tell the whole story in the article The Trojan Room coffee pot: the first webcam. In 1994 came QuickCam, a small round camera that shot black-and-white video at a resolution of 320 × 240 pixels and cost 99 dollars. Its production was later taken over by Logitech.
How it works
A webcam has a lens, a CMOS image sensor and a chip that compresses the picture and sends it over USB. The sensor relies on the photoelectric effect explained by Albert Einstein. Today's cameras offer Full HD or 4K resolution, and some can use artificial intelligence to blur the background or track a face.
Privacy
An attacker who takes over a computer can switch the camera on too. That's why laptops have an indicator light next to the camera, and many also have a sliding cover. A sticker over the camera isn't paranoia — plenty of security experts use one too. You can read more about protecting yourself in the article cybersecurity.
Webcam versus security camera
A webcam is built for video calls and only works while it's connected to a computer. A security IP camera runs continuously, records to a recorder or NAS, sees in the dark, and can sit outside through rain and frost.