what is the meaning of "breakbuilding" in snooker

建立单杆高分

see it
in http://members.aol.com/snookermag/breakpak.gif
In order to continue a break, it is often necessary to dislodge some reds from a closely packed bunch. Beware - only try this if you are an equally good or better potter than your opponent. Otherwise it could be disastrous! It is usually advisable to break the pack when potting a colour, the most popular being black or blue. In shot A, finish on the black about parallel with the top cushion. Pot the black and screw into the pack. This is more difficult if the top reds are in a line across. In shot B, finish below the black and rebound from the top cushion into the pack. Shot C shows a pot on the blue, stunning full-ball into the pink, which breaks the reds. Beware of hitting the pink too thin, as an in-off often results! In shot D, pot the green and come off the side cushion. Some screw and right-hand sid