What does 0.0.0.0:* mean in netstat?

The column after local address is "Foreign Address" - as these are UDP ports, and listening ports, there is no foreign address so a wildcard is shown.

I'm not sure if this would show the other end(s) if packets had been received as UDP is a connectionless protocol. Also as one-many comms is allowed a single foreign address could be misleading. So it may ALWAYS show the wildcard for udp.

If it says 0.0.0.0 on the Local Address column, it means that port is listening on all 'network interfaces' (i.e. your computer, your modem(s) and your network card(s))