Most traditional planes (standard angle) are bevel down, with the cutting angle being determined solely by the plane bed. The newer planes (Such as those offered by Veritas…my personal favorites 
) are offered in a bevel-up configuration. The advantage to the bevel up planes is that the effective presentation angle of the blade is determined not only by the bed angle, but the bevel grind angle as well. In short, with a single bevel-up bench plane, you can go from a 25 degree low-angle plane, to a 38 degree normal plane, to a 50 degree high-angle plane simply by switching blades. With a bevel down plane you are limited to whetever they set the bed angle at.
Ryan
) are offered in a bevel-up configuration. The advantage to the bevel up planes is that the effective presentation angle of the blade is determined not only by the bed angle, but the bevel grind angle as well. In short, with a single bevel-up bench plane, you can go from a 25 degree low-angle plane, to a 38 degree normal plane, to a 50 degree high-angle plane simply by switching blades. With a bevel down plane you are limited to whetever they set the bed angle at.Ryan
