Bull flag
A bull flag begins with a strong upward move that forms the pole, followed by a brief period where the market drifts sideways or slightly downward in a narrow channel. This channel is the flag. The structure shows that buyers pushed price aggressively upward, then paused while sellers could only create a shallow pullback. When price eventually closes above the upper line of that small channel, the market confirms that buyers have regained control. The typical expectation is that the market will continue in the direction of the original pole, often traveling a distance similar to the height of that pole.
Bear flag
A bear flag is the same structure in reverse. Price falls sharply to create the pole, then enters a controlled drift upward or sideways inside a narrow rising channel. This flag shows that buyers do not have enough strength to push price back meaningfully, even after a large selloff. When price eventually closes below the lower boundary of the channel, the downtrend is considered ready to continue. The projected move is usually estimated by repeating the length of the original pole downward from the breakdown level.