When you launch an EXE file, PowerShell will happily start it, then continue and not care about it anymore:
PS C:\> notepad
PS C:\>
If you'd like to keep a handle to the process, for example to find out its process ID, or to be able to check back later how the process performs, or to kill it, use Start-Process and the –PassThru parameter. This returns a process object:
PS C:\> $process = Start-Process -FilePath notepad -PassThru
PS C:\> $process.Id
5936
PS C:\> 'You just launched process {0}.' -f $process.Id
You just launched process 5936.
PS C:\> 'CPU consumption in seconds so far: {0}.' -f $process.CPU
CPU consumption in seconds so far: 0.1092007.
PS C:\> $process.CloseMainWindow()
True
PS C:\>