Your '97 Honda Accord's wheel speed sensors are a part of the car's anti-lock brake system (ABS). Each sensor monitors the speed of each wheel to help determine whether ABS-assisted braking should be activated during a stop. The sensors judge speed differently than the speedometer.
A toothed ring is mounted on the axle hub. As the ring turns with the wheel, its teeth help generate voltage with the speed sensor's magnetic core and coil windings. The frequency of the voltage pulse is monitored by the ABS control module, where it exists as a digital signal indicating wheel speed. A change in one wheel's speed vs. the other wheels indicates to the module which wheel is losing traction during braking, and to apply ABS-assist.
The speed sensors are located on the steering knuckle, behind the rotors of the wheels. They are securely attached by two bolts and connect to wire harnesses that are protected by a metal tube along the control arm.
Replacing the sensors is not difficult. You can do the job yourself with basic hand tools and new wheel speed sensors. Just be sure to purchase the correct sensors for your 1997 Accord.
