Learn in the textbookOrganizational Structures
DefinitionA holding company (持株会社) controls other companies as subsidiaries by owning their shares, and brings the whole group together.
ExplanationOne that runs no business of its own and concentrates on group strategy and management is a pure holding company (純粋持株会社), while one that runs its own business as well as owning subsidiaries is an operating holding company (事業持株会社). Many put "Holdings" (ホールディングス) in their company name.
AnalogyIt is like a driver holding reins made of shares, keeping several separately running carriages headed the same way.
Memory hookHolding simply means owning, which is where company names ending in Holdings come from.