How does threading in powershell work?

I want to parallelize some file-parsing actions with network activity in powershell. Quick google for it, start-thread looked like a solution, but:

The term 'start-thread' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included, verify that the path is correct and try again.

The same thing happened when I tried start-job.

I also tried fiddling around with System.Threading.Thread

[System.Reflection.Assembly]::LoadWithPartialName("System.Threading")
#This next errors, something about the arguments I can't figure out from the documentation of .NET
$tstart = new-object System.Threading.ThreadStart({DoSomething}) 
$thread = new-object System.Threading.Thread($tstart) 
$thread.Start()

So, I think the best would be to know what I do wrong when I use start-thread, because it seems to work for other people. I use v2.0 and I don't need downward compatibility.