Finding parameter values

I am very new to powershell. If this question doesn’t make sense maybe someone can explain what I am missing.

How do you discover available values for a parameter? For example:

Invoke-TroubleshootingPack [-Pack] <DiagPack>

How do I find out what values are allowed for -Pack? I have been searching through powershell help and google and I can’t seem to find an answer. This probably means I am completely misunderstanding something, so hopefully someone here can explain this to me.

Thank you!