AI Servo AF is one of up to three autofocus modes and is found on all Canon EOS cameras. It’s designed for shooting moving subjects.
On DSLR cameras it’s called AI Servo AF; on mirrorless cameras it is simply Servo AF.
This mode continually checks and refocuses the lens each time the camera-to-subject distance changes, right up to the moment of exposure. This makes it ideal for photographing moving subjects – you can retain partial pressure on the shutter button as you follow the subject with the camera, applying full pressure to take a picture at the key moment.