2006 Toyota Camry Small 3-4 vibrations when brakes were app

I have 2006 Toyota Camry SE. Its mileage was 54,000. When I apply brakes on normal road, most of the time, it is normal stop. But, when I apply complete brakes slowly on snow and salty area, the car is giving small 3-4 vibrations. What is the reason for those jerks. Somebody told me that it is mainly due to anti-lock system brakes (ABS), where wheels won't stop quickly and will lock at different pressures and times. Please answer to the above problem of vibrations after hard brakes.