Because it represents an area where orders are accumulated by buyers (the market turns bullish).

The chart in the image:

• The chart shows Japanese candlesticks with areas marked as Bullish OB (Bullish Order Block).

• These areas are highlighted in light green, indicating a strong upward move ahead.

• The label 'High Violated' indicates that the high price of a certain candle has been breached, confirming that this area is a Bullish Order Block.

Why are Order Blocks used?

• Entry Points: Traders use Order Blocks to identify potential buying areas (in the case of Bullish OB) or selling areas (in the case of Bearish OB).

• Support and Resistance: These areas often act as future support or resistance levels.

• Understanding Market Behavior: Order Blocks show where institutional investors (smart money) have accumulated their orders, resulting in a price direction change.

Simple Summary:

A Bullish Order Block is an area on the chart that appears before a bullish move.