This means that you can order food, medicine, pet supplies and more from stores like Whole Foods, Costco, Walgreens, PetSmart and Bed, Bath & Beyond. Currently, Google Express shopping offers access to over 50 retailers for same-day delivery in every state in the US except for Alaska and Hawaii.
Unless you have a $95 annual membership, there's usually a minimum order amount and a delivery fee associated with Express. However, when you have Google Home lend a hand between now and April 30th, you won't have to worry about paying any membership or service fees. All you have to do to get started is input your payment info and shipping address in the Settings menu of the Google Home app.
Update: This post has been updated to clarify where Google Express is available.