Magisk ("Magic Mask") is one way to root your Android device. It's specialty lies in the way the modifications on the system are performed. While other rooting tools alter the actual data on the system partition, Magisk does not (which is called "systemless"). This enables a way to hide the modifications from root-sensitive applications (e.g. for banking or games) and allows using the official Android OTA upgrades without the need to unroot the device beforehand.
You can get familiar with Magisk reading the official documentation on GitHub. If you don't have Magisk installed, you can find installation instructions in the documentation. If you use an official Android version and plan to upgrade it, Magisk provides a tutorial on GitHub.
Learn more about rooting your device with Magisk.