You can still make outgoing calls while Call Forwarding is active. However, because all incoming calls are transferred immediately, you can't answer incoming calls on your original line when this feature is activated. If there are only some numbers you want to have forwarded, use Selective Call Forwarding instead.
You will hear a short ring on the original phone each time a call is forwarded. The number receiving the forwarded call then rings normally.
If you forward calls to a long distance or toll number, you'll be charged applicable rates.