ParameterSet1.ps1

Function MyFunction
{
    [cmdletbinding()]
    
    param([parameter(Mandatory,ParameterSetName="ServiceSet")]$service,
          [parameter(Mandatory,ParameterSetName="ProcessSet")]$Process,
          $Test)
          Write-host "Service: $service" -ForegroundColor Green
          Write-host "Process: $process" -ForegroundColor Yellow
          Write-host "test: $test" -ForegroundColor Magenta
}

write-host "about to call with -service" -ForegroundColor Cyan
MyFunction -service alg -test hi
write-host "about to call with -process" -ForegroundColor Cyan
MyFunction -Process powershell -Test bye

write-host "about to call with -service and -process" -ForegroundColor Cyan
MyFunction -Process powershell -service alg -Test oops

write-host "about to call with NO PARAMS -- we will show you how to fix this soon" -ForegroundColor Cyan
MyFunction