With Android 9 Pie, Google rolled out a new feature called "App Actions". These are actions that will appear in the app drawer below the top row of apps (which are your most commonly used apps) and the rest of your apps. These app actions are actionable, and will vary over time, as the operating system learns what you do on your phone at each time of the day, and on which days. So these will change, to hopefully, help you get things done on your smartphone faster.
App Actions are turned on by default, and will show only two actions by default. There's no way to change the number of actions it shows, but you can turn off App Actions if you wish to do so. This is done by long-pressing on your home screen and tapping on settings. Then tap on Suggestions. The second toggle will be for App Actions. You can flip that toggle off if you want to turn it off.
As mentioned already, these actions will vary based on the time of the day, and the day of the week. So in the morning, you may get an App Action that shows you the "For You" section of Google News. And perhaps another one for "Pay" using the Starbucks app, if you go to Starbucks each morning before work. Now some of these actions may not be something you want in the app drawer. In which case, you can long-press it, and move it up to "Do Not Show" on your home screen, and it'll stop showing that action. In the same vein, you can also move it to your home screen, so that you can easily hit that action whenever you want, without waiting for Android Pie to show it.
For the most part, App Actions aren't really customizable. This is because they rely on machine learning and artificial intelligence, once it learns how you use your smartphone each day. Now if you do think that the actions that your phone shows you is inaccurate, you can remove them. But unfortunately, you can't add in your own actions there to do what you'd like. That might be something that Google adds in a future version of Android, but for now, that's not a choice. App Actions can be very useful, especially if you use your phone pretty much the same way each day, and the more you use your phone, the better App Actions will get.