Alphabet is the name of Google's parent company, established during the 2015 restructuring that created a major market-cap company.
Google announced the Alphabet restructuring in August 2015, and Alphabet Inc. became the public parent company in October of that year. Google remained the largest subsidiary, containing businesses such as Search, YouTube, and Android.
The reorganization separated Google's core internet products from more experimental or specialized ventures. Alphabet's other businesses have included autonomous-vehicle company Waymo, life-sciences company Verily, and research organization X.
Alphabet did not replace Google as the name of the search engine or the consumer brand. Google also remained the name of the operating subsidiary that handles the company's main online products. The corporate change affected ownership and reporting structure rather than turning the search engine itself into a new service.