Alphabet is the parent company created in 2015 to oversee Google and several other businesses.
Google announced the corporate reorganization in August 2015, and Alphabet became the publicly traded parent company in October of that year. Under the structure, Google became Alphabet's largest subsidiary, while activities such as life sciences and investment projects could operate as separate units.
The reorganization separated Google's core internet products—such as Search, YouTube, and Android—from newer or more experimental ventures. Larry Page became Alphabet's chief executive, while Sundar Pichai became Google's chief executive at the time of the restructuring.
People sometimes use “Google” and “Alphabet” interchangeably, but they are not exactly the same corporate entity. Google is the principal operating subsidiary; Alphabet is the holding company whose shares are publicly traded under ticker symbols including GOOGL and GOOG.