Up cut refers to the direction of the flute. As the router bit grooves, slots and cuts the chips are forced upwards. Therefore, the best finish is on the underside of the cut part. Up cut spirals are not recommended for softer materials such as MDF as the finish on the top surface is often ragged. Up-cut spirals can run at higher speeds but requires good quality suction on table to prevent material tug.
Three flute router bits have a smooth cutting action and a greater finish in harder materials. Three flute router bits last longer, run faster feed rates and are less susceptible to breaks than one and two flute router bits.
The chipbreaker geometry refers to the notches in the cutting edge. These notches shorten the chips produced, which reduces the amount of heat caused by friction and increases the longevity of the tool. The notches are offset so you aren’t left with lines on the board. The following edge removes any remaining material and the finish left behind is close to perfect. However, there is a slight coarseness left behind by the corners of the notches that dig into the material.