While there are probably wrinkles^, the gist is that instead of 100% of waymo shares being owned by Alphabet, there are now 2.25B/current_valuation % shares owned by the external investors. Alphabet shareholders now own (1-x%) of Waymo, but it will continue to be consolidated on Alphabets financial statements.

^ wrinkles might include different share classes of Waymo, rather than Alphabet stock, debt-like provisions that make the investment less like common stock ownership