The command line help powershell.exe /? covers this:
-Command
    Executes the specified commands (and any parameters) as though they were
    typed at the Windows PowerShell command prompt, and then exits, unless
    NoExit is specified. The value of Command can be "-", a string. or a
    script block.
    If the value of Command is "-", the command text is read from standard
    input.
    If the value of Command is a script block, the script block must be enclosed
    in braces ({}). You can specify a script block only when running PowerShell.exe
It shows an example at the end:
EXAMPLES
    PowerShell -PSConsoleFile SqlSnapIn.Psc1
    PowerShell -version 1.0 -NoLogo -InputFormat text -OutputFormat XML
    PowerShell -Command {Get-EventLog -LogName security}
    PowerShell -Command "& {Get-EventLog -LogName security}"