What Is the Role of the ‘Target’ in the Bitcoin Difficulty Adjustment?

The 'target' is a 256-bit number that dictates the maximum value a block hash must be less than or equal to for the block to be considered valid. The difficulty adjustment algorithm manipulates this target.

A lower target means a higher difficulty, requiring miners to find a hash with more leading zeros, thus requiring more computational effort (hashes) on average to find a valid block.