When you use a web host, you pay somebody else to store all the files for your site and they give you a certain amount of bandwidth a month. You can find some really low priced ones nowadays.
Hosting your own web site is pretty easy, but bandwidth is usually a problem when you run it from you house. Your upload speed is usually only ~256Kb's. Just go w/ a web host, they're so cheap these days.
I would NOT use Geocities to host a site. Use something like
GoDaddy.com or look on
WebHostingTalk you'll find lots of info there on the subject.