You go online and when you search your searches go through the proxy and then out into the internet.
School/work however likely hasn't blocked all sites, and this is where online proxies come in. You go onto a site, enter the URL (web address) you want and that site will then go to the site for you and display it. So you never actually visit that site, they can't catch you, unless they catch you in person xD
If that's not clear enough, just try it out. If you have any questions just post them and i'll get back to you.
Here are two proxies that i've used and know work here.
If these are blocked (i'd be surprised) then try any of the ones on this site.
P.S. Try not to get caught or they'll just block the proxies. Also don't look at porn in school, it's just a stupid thing to do :)