Tsumego (詰碁) is the Japanese term for a type of go problem based on life-and-death.
Tsumego problems are common in newspaper columns.
Tsumego problems have been found in Chinese books dating back to around the 13th century.
They range from situations that occur quite commonly, which every strong player ought to be familiar with, to deliberately difficult puzzles.
Solution diagrams will either show the most tenacious resistance that the opponent can offer, or lines that require interesting or tricky tactics.