Cameras can end an exposure with a physical mechanical shutter or by reading the sensor electronically. The difference matters for sport, flash and lighting.
Mechanical shutter
A physical curtain exposes the whole frame quickly, so moving subjects don't distort. It's audible and wears over time (often rated at 200,000-500,000 shots).
Electronic shutter and rolling shutter
An electronic shutter reads the sensor line by line. If that takes a long time, fast subjects lean or bend and LED lights can show bands. We list this as the readout time on each camera page: roughly 60ms and slower is risky for action, 20ms is good, and under 10ms behaves almost like a mechanical shutter.
Stacked and global shutters
Stacked sensors (in cameras such as the Nikon Z8, Nikon Z9, Sony A1, Sony A9 II, Canon EOS R3, Canon EOS R1, Fujifilm X-H2S and OM System OM-1) read out fast enough for silent sport shooting. The Sony A9 III's global shutter reads the whole sensor at once, with no rolling distortion at all.
What this means for buying
If you shoot sport with a slower-readout camera, use the mechanical shutter and you'll be fine. Pay for a stacked sensor if you need silent shooting of fast action, very high burst rates or the best video.