D/r all

Pls ans me some query

1. Why used this folder /etc/rc.d/rc.local in proxy server(fedora)?
2. What does it mean that iptables -F, iptables -t nat -F, iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE, -t nat -A PREROUTING -i eth1 -p tcp --dport 80 -j REDIRECT --to-port 3128

Thanks