Okay, some uber geek will come along and more articulately explain all these bells and whistles, but I’ll give you my (semi-clueless) interpretation:
These are all email related, I believe. POP3 email is cool, because you can set your own email account, like, for instance, “Lolababy@yourdomain.com” and then you set it up so you can send and receive email through Outlook Express or other email program. You could give a jillion email accounts to your friends, all with @yourdomain.com. Cool.
Forwarders, I believe, are when you set up a sort of dummy email account and when someone mails something to that address, it is actually forwarded to another account—your yahoo account, for instance. There might be other uses for forwarding as well. Never used it much.
I think filters are related to spam control. (Guessing.)
Don’t know. Just sounds like various web mail types.
I only know a teeny weeny bit about this: PHP 4+, Perl, JSP and other scripting languages are sometimes used for forms (fill in the form, send it to the webmaster, etc.) and other more interactive stuff. I only learned enough to do a simple form in ColdFusion (another one of these kinds of languages).
Uhhh…databases are for when you’ve got a TON of information and you don’t want to hand-code a straight HTML page for each page or piece of information. So you set up a database with all the different things (pictures, paragraphs of information) and then people can search for the information and through some form of magic I don’t understand (using a scripting language like Cold Fusion) the page with the requested information is served up. This is way over my head, though.
You can buy additional domains and set it up so visitors will be sent to your main domain. So, you can set up www.anotherdomain.com and it’ll be automatically directed to www.mydomain.com. At least that is my understanding.
subdomain.mydomain.com. I think.
This is cool. You can give ftp accounts to other people, so they can log on with WS-FTP (or Fetch, or whatever ftp program they want to use) and send up files to their FTP space. And others can download files from their space.
You know as much as I do about this. Seems pretty straightfoward, though.
You know those cool “404 Not Found” pages that are funny, colorful, have cute messages, and what have you? Well, you can do that. You don’t have to settle for the boring black and white plain text 404 page.
For simple image hosting, www.pair.com has a simple plan for image hosting and I think it’s pretty cheap. Check their site for more info.
I also use www.readyhosting.com, which gives 500 mb of space (which is plenty) and has a lot of the goodies (but not all—and different ones) than what you list above. I’m pretty happy with them.
To use most of these hosting services, you’re going to have to get used to using an FTP program to upload your files. WS-FTP for Windows is free, but I never liked it much. Fetch for the Mac has an old freeware version, and I like that much better. If you don’t know how to write or create web pages and you want to, go to www.htmlgoodies.com right now and start learning!
Good luck to you! 
