In the midst of Google's largest product announcement ever, a brand new app turned up in the Play Store with the name Google Assistant. You might be thinking that this will finally bring Assistant to Android tablets, or maybe even enable it on Chromebooks, especially since the Play Store allows installation on both types of devices. Unfortunately, it doesn't do either of these things. The app is just a shortcut to trigger Assistant on devices that already have it. Yes, it does the same thing as holding the home button.
Note that the Play Store listing begins with a paragraph that says most of what you need to know about it, and follows with a pair of footnotes that probably deserve to be at the top.
The Google Assistant app provides another way to launch the Assistant that’s already available on your phone. It allows you to quickly access your Google Assistant with one tap. You can still access your Assistant by pressing and holding down your home button or by simply saying, "Ok Google."
* Your device must still meet the requirements in order to use the Google Assistant (Google Search v7.11 or higher and minimum memory requirements).
* You do not need this app to use the Google Assistant if you already have the Google Assistant on your device.
Technically, it's a little more than a shortcut, as an examination of the code shows that it also checks if a device is eligible for Assistant, and informing users if it is not. Aside from that, the app doesn't do anything of substance.
In essence, the new Google Assistant app is currently just a shortcut you can place on your launcher. This probably won't interest the vast majority of people, but it may still hold value for anybody that uses automation tools or utilities to launch apps. For those people, this will be useful to wake up Assistant with a gesture or as part of a script. However, it's not like there weren't already other ways to do this, but maybe Google is providing its own version for simplicity.
The APK is signed by Google and upgrades your existing app. The cryptographic signature guarantees that the file is safe to install and was not tampered with in any way. Rather than wait for Google to push this download to your devices, which can take days, download and install it just like any other APK.