Front squats do target the quads a little more, but if you focus on really sitting back into your heels, they can also target the glutes and hams equally well. Holding the weight in front helps aleviate some of the stress on the vertabrae and back muscles that happen when you put a heavy bar on your back. For me, I'm somewhat restricted in the weight I can squat because of what I can safely lift over my head. When I hold the weight in front I can lift far more weight because the over-the-head lift is eliminated. It took some practice to find the most comfortable position for holding the weight in front, but it has worked wonders for my squatting weight!