The `kwin` package in Ubuntu is part of the KDE Plasma desktop environment. It's the window manager for KDE, responsible for managing the placement and appearance of windows.
To install `kwin` on Ubuntu, you can use the following command:
```sh
sudo apt update
sudo apt install kwin
```
If you want the full KDE Plasma desktop environment, you can install it with:
```sh
sudo apt update
sudo apt install kde-plasma-desktop
```
After installation, you can select the KDE Plasma session at the login screen.
