It means when the market is sideways and bouncing within a channel. It is when bulls and bears are still indecisive. Depending on fundamentals as well, this is when smart money starts to accumulate. Big funds usually accumulate in these channels because they need time to accumulate. They act as the bulls here. The bears will usually be those day-trading euphoric shorters trying to scalp every bounce, or just some random capitulation. This is the time when money fears to go in and those who have held already gave up on going out. The volume will be quite low.