Zero point
The zero point is the level at which traders trapped on the wrong side get back to zero profit. Trapped buyers sell there and trapped sellers buy there, so price often reacts at it.
If price builds an accumulation above a level and then falls below it, the traders who bought in the accumulation are trapped buyers. When price comes back up to the level, they are at zero, and many sell to get out. The mirror case, an accumulation below a level followed by a rise, leaves trapped sellers who buy back at the zero point.
Learn more: the four market players.