Learn in the textbookSets and Logical Operations
DefinitionA Venn diagram (ベン図) draws sets as circles and shows how they relate through the circles' overlap and position.
ExplanationThe outer rectangle stands for the whole under consideration; inside a circle is that set, and outside is its complement. Two circles split the whole into 4 regions and three circles into 8, and each region is fixed uniquely by which circles it lies inside and which it lies outside. Turning a shaded region into words or an expression lets you check by eye how the conditions are put together.
AnalogyLike circling the areas of two towns on a map and treating the houses where the circles overlap as belonging to both towns.
Memory hookIt is named after the British logician John Venn, so the name is a person's, not a description.