That depends on your VPN and how the routing is configured - there is no single answer that is always correct.
The simplest way to check, other than by asking your work's IT staff who manage the VPN, is to check the default gateway (
netstat -rn at a command prompt - look for a destination of
0.0.0.0). If the gateway is on your home network then your Internet traffic goes out your home connection. If the gateway is on the VPN then it goes out your work's connection.
Based upon your comment it sounds like your work's VPN is trying to route all traffic across it. I'm not certain what will happen since with 2 default gateways the
metric will control which route the traffic takes. Without further information I would assume that all traffic is going across your work's link when you're connected to the VPN.