* What was called "Google" will now be called "Alphabet", with Larry and Sergey as CEO and President.
* Much of the core business of the old Google will be operated in a division/subsidiary of the new Alphabet called "Google", of which Sundar Pichai will be CEO.
* The rest of the old Google's business will be in other units of Alphabet.
They are refactoring. Google is being updated to make some of its sub-classes into new top-level classes (sharing some characteristics with Google) and retain the rest as sub-classes. But to do this it must create a new parent class (for Google, and all of the other newly promoted classes) which is the new Alphabet class.
I find it easier to think of it as a name change and the creation of a new subordinate entity within the old organization with its own CEO than to think of it as creating a new entity above Google, and transferring lots of functions from Google to the new superior entity, transferring all stock in Google to stock in the new superior entity, and changing the leadership of Google.
* What was called "Google" will now be called "Alphabet", with Larry and Sergey as CEO and President.
* Much of the core business of the old Google will be operated in a division/subsidiary of the new Alphabet called "Google", of which Sundar Pichai will be CEO.
* The rest of the old Google's business will be in other units of Alphabet.