Frame rate
Also called fps · frames per second
Frame rate is how many images a camera sends each second. Webcams commonly run at 30fps and many drop lower in dim light because each frame needs a longer exposure.
In practice
Most webcams aim for 30 frames per second, which looks smooth in a call. In dim light many drop to 15 so each frame can be exposed longer, which looks choppy. A low frame rate in the camera itself is different from choppy video caused by a slow internet connection during a call.
How to check
The webcam test counts the frames that actually arrive in the browser, with no network involved. If it shows about 30, the camera is fine and choppiness in calls comes from the connection. If it shows about 15, add light in front of you and test again.