Canon EOS REBEL T7I Basic Instruction Manual page 137

Servo AF for Moving Subjects
This AF operation is suited for moving subjects. While you hold
down the shutter button halfway, the camera keeps focusing on
the subject continuously.
When the drive mode is set to <o> for high-speed continuous

shooting, the maximum continuous shooting speed is approx. 4.5
shots/sec. The pictures will be taken with priority given to the
continuous shooting speed.
When the drive mode is set to <i> for low-speed continuous

shooting, the maximum continuous shooting speed is approx. 3.5
shots/sec. The pictures will be taken with priority given to subject
tracking.
For flash photography, the continuous shooting speed will become

slower. Regardless of the <o> and <i> settings, the continuous
shooting speed will be the same (max. approx. 2.0 shots/sec.).
When focus is achieved, the AF point will turn blue.

The exposure is set at the moment the picture is taken.

When [AF method] is set to [u+Tracking], focusing will be

continuous as long as the Area AF frame can track the subject.
Changing the Autofocus OperationN
135