Start-Job -ScriptBlock {Get-EventLog -LogName System}
Invoke-Command -ComputerName S1 -ScriptBlock {Get-EventLog -LogName System} -AsJob
Invoke-Command -ComputerName S2 -ScriptBlock {Start-Job -ScriptBlock {Get-EventLog -LogName System}}
Get-Job

Id     Name       PSJobTypeName   State         HasMoreData     Location        Command
--     ----       -------------   -----         -----------     --------        -------
1      Job1       BackgroundJob   Running       True            localhost       Get-EventLog System
2      Job2       RemoteJob       Running       True            S1              Get-EventLog System

$Session = New-PSSession -ComputerName S2
Invoke-Command -Session $Session -ScriptBlock {Start-Job -ScriptBlock {Get-EventLog -LogName System}}
Invoke-Command -Session $Session -ScriptBlock {Get-Job}

Id     Name            PSJobTypeName   State         HasMoreData     Location             Command                   PSComputerName
--     ----            -------------   -----         -----------     --------             -------                   --------------
1      Job1            BackgroundJob   Running       True            localhost            Get-EventLog -LogName Sy… S2