WD Media Player - any lag when streaming from a PC?

I have a media player connected to the TV via HDMI.

It's a 'Western Digital TV Live Network Media Player' (so it says on the box).

Model number is WDBAAP0000NBK-AESN.

It doesn't have a built-in streaming facility like some models, but it will accept a USB WiFi connector that will presumably link to my several PCs via our broadband modem.

Question:

1) Anyone know how this streaming works? I mean, do they stream directly - like, in real time - or do they buffer the data stream via ram to avoid lag.

And before you suggest I ask Western Digital, I tried that. But I was never much good at understanding Chinglish Geekspeak. So I'm hoping someone out there has had experience with this type of media player.