In distillation, 'heads' are the first vapours to condense — highly volatile compounds including methanol, acetone, and other low-boiling-point substances that are unsafe or unpalatable in finished spirits. 'Tails' are the last fractions, dominated by heavier alcohols (fusel oils) and water; these are also typically removed.
Between heads and tails sits the 'hearts' — the clean middle fraction that becomes the bottled spirit. The skill of the distiller lies in deciding precisely when to cut from heads to hearts, and from hearts to tails. Industrial distilleries use sensor-driven automation for these cuts; traditional craft distillers cut by hand, by nose and taste.
Tannenblut's heads and tails are cut by hand. The decision is made by the cellar master at the still, not by an automated sensor.