WSUS for remote clients

We have WSUS 3.0 and all of our clients are on the domain, including our remote clients. None of our clients have local admin privledges. our AU policy is GPO based and updates need to be approved on the WSUS before installationon the clients. I want to know how our remote employees receive their updates from the WSUS or from the internet.

1.How do the remote clients communicate with the WSUS for downloads, through the VPN? How does that work, once the update is approved, the client logs onto the VPN and they are told by he WSUS what updates are aproved and then they download/install those updates from the internet or the WSUS?

2. How can I configure the remote clients to communicate with the WSUS while they are not on the VPN? At leasst to communicate what they are approved to download then download it from the internet directly?

Thanks!