high impedance, low impedance?

I could use some wiring help here. I'm not that good at the terminology but I
know that and always ask advice, so things usually turn out right.
Question; I'm wiring in a used DME and the ident (audio) output has a choice of
'high impedance out' or 'low impedance out'. What's the difference? Is one for
direct to headset and the other for going through the amp in the nav/comm
receiver or something like that? Thanks in advance.

Jim