Squat stands (or squat racks as others call them) are a necessary equipment for serious weight trainers. The squat stands allow the lifter to take the barbell on his shoulders from an almost standing position.
This is the safest way to position the barbell on your shoulder if you're doing a set of squats. Squats recruit some of the biggest muscles (lower back, quads and hamstrings) of the body and so will allow you to lift heavy weights.