How add to home screen works
A browser can install a web app directly: the site declares an icon, a name and a start address, and the browser creates a launcher. There is no store account, no download and no review. The trade is that the app has browser capabilities rather than native ones.
The mechanism is ordinary and most people have never used it deliberately, because nothing prompts them to. It is worth knowing because it removes an intermediary from the chain.
What the site declares
A small file lists the name, the icons, the colour and the address to open. The browser reads it and offers to install. Nothing is downloaded in the sense of a package: the icon points at the site, and the files are cached the way any site's files are.
What you get
An icon on the home screen, a window without browser controls, and the app in the task switcher. For a chat that is essentially the whole experience, which is why this route works so well for this category and less well for a game.
What you do not get
The capabilities that need a native app: background work, deep system integration, and features a browser deliberately withholds. For a chat none of these are used, which is what makes the trade painless here and painful elsewhere.
Removing it
Delete the icon and it is gone, with no account to close and no residue beyond ordinary browser cache. This symmetry is the quiet benefit: the thing that installs in 2 taps also leaves in 1.
Questions about the app
Does it update itself?
Yes, because it is the site. There is no update to approve and no version to be stuck on.
Does it work on both major platforms?
Yes, with different wording in the menu and slightly different capabilities. The icon and the window behave the same.
Is it really an app?
It behaves as one for the purposes people care about. Arguing about the definition matters less than what it does on the screen.
Open the browser menu and choose add to home screen.
Open the chat first