Each process running in Windows is assigned a unique decimal number called the process ID (PID) to identify an active process. This number is used to specify the process when for example attaching a debugger to it.
By default, all File Explorer windows, including the desktop shell, run in a single explorer.exe process. If one File Explorer window hangs or crashes, it will cause all File Explorer windows running in the same process to hang or crash until the process restarts.
You are able to use the Open in new process context menu to manually open folder windows (File Explorer) in a new process.
If you like, you can enable to launch folder windows in a separate process by default. This way each explorer.exe process will have its own process ID (PID) to improve stability of the explorer shell.
This tutorial will show you how to enable or disable to launch folder windows in a separate explorer process by default for your account in Windows 7, Windows 8, and Windows 10.