Releasing release your IP address from your computer, so it would drop your connection. Renewing will give you an IP address again, restoring your connection. Usually you can hit renew or renew all and it will release and renew. The renew all will try to renew the IP's for everything (say if you have a network card and a modem), renew will just renew the IP for whatever device you have highlighted in winipcfg. However, with cable modems, you usually are assigned the same IP for a while, I can sit here and release and renew my IP 20 times if I wanted, and I will get the same IP back (for about a month). If you do plan on staticing an IP make sure it is allowed, ISP's look down on that, and will usually cancel your service when you are discovered.