The options are AllSigned, ByPass, Default, Remote Signed, Restricted or undefined
You can read about each of these by typing in the following command:-
Get-Help Set-ExecutionPolicy -online
This will load the online help for this command, if your ever needing help with PowerShell then you can search for help like so, Get-Help *services*, this will show you what commandLet’s are available for working with Services, i.e. starting them stopping them and so on.
I set the execution policy to RemoteSigned so that I can run my own PowerShell scripts but ones I download from the internet wont run unless I change the setting, so that my system is secure from any unwanted side effects from other peoples scripts.