A Smith machine features a barbell that is fixed within steel rails, allowing only vertical movement. This provides a stable and controlled environment for lifting, which is ideal for individuals working out alone or those who want to focus on form without balancing the weight. On the other hand, a squat rack is an open framework that holds a free-moving barbell. It allows for a full range of motion, including both vertical and horizontal movements, giving the lifter the freedom to perform a wider variety of exercises and engage more stabilizing muscles.