Black Point Compensation
A conversion option that maps the source's darkest tone to the destination's darkest tone rather than clipping it.
In depth
Paper cannot reach the black a screen displays, so without compensation every tone darker than the paper's maximum density is clipped to solid black and all shadow separation is lost. Compensation scales the whole tonal range instead, preserving gradation at a small cost in overall contrast. It should almost always be enabled for photographic printing.
Examples in practice
Enabling it restores visible folds in a black dress that had printed as a single flat shape.