Finding valid values of a Parameter name in Powershell

I am a beginner in PowerShell. I was working with this command:

Get-EventLog -Logname Security

Is there any place PowerShell help or otherwise that lists all the valid values of the Logname parameter. I think the following are valid "-Logname" values - Security, System, Application etc...

Furthermore, for any other command that expects a pre-made set of value for a Parameter, what source do I go to to find them. Again using the same example as above, where do I find listed "Security, System, Applcation" as valid values for Logname Parameter.

Thanks.

KMD.