Running / Maitaining a server?

Right guys and girls,

I have a few questions i need answering about servers, I have just downloaded and installed apache on my computer, which is just a case of trial purpose! I dont intend on using this as a 24/7 server. Right now down to the core questions:

1. At the moment i can access my files on the internet, if i had a proper server how would i go about "getting" domains for the server?? I mean, for example if i made a site for myself or another person, how would the domain be implemented?

2. How are servers kept online all the time? What happens if i wanted to change ISP and i would normally be offline for a few days.

You would have to register the domain somewhere and have it point to your ip.
Some places offer DNS for dynamic IP's.

The servers are kept online all the time because the computers or datacenters they are hosted on are always switched on and are online.

If you wanted to change ISP's then the server would be offline during that time.

Right i see, where would one go about (and how) getting a domain pointed to an IP?

You can get a free subdomain redirect from http://www.no-ip.com .

Or you can get a TLD that will work on a dynamic ip from http://www.changeip.com/ddnsinfo.asp