1) If I edit or add a page or a post locally, how do I get that part of my localhost database synchronized with the onlinehost database?
You'd have to import the files through your database, and put them on the regular server. I don't know if I'd recommend doing that, though - it's possible you could mess up the whole site (I only say that because I've only done it a couple of times - with success, but barely - I'd be wary of doing it)
2) If someone comments online, how do I synch that with my localhost database?
There's no "synching". It's the same as above - you'd have to copy the database files to a file, then update the database on the regular site.
3) What do all these links that say RSS feed for this topic do?
RSS Feed is the feed to the topic. (Man that wasn't clear, was it?) RSS is syndication. You can be updated when the site is updated (for a sitewide RSS feed) or if you're watching a particular topic, you can link to the feed and be notified immediately when a new post had been added. Google RSS to find more info on it.
4) I am reasonably comfortable with FTP Lite. Do I also need to learn the intracacies of phpmyadmin. What are the features of each? Do they overlap? Do I need both? What do mysql and apache do?
FTP is how you upload and download files from a server. phpMyAdmin is how you access your databases and edit the information. MySQL is your database. Apache is how PHP and MySQL run. FTP has aboslutely nothing to do with phpMyAdmin, PHP (a programming language), MySQL and Apache. It's something you use to manage your filesystem on your server.
5) When I first started, there was an xampp control panel that showed what was running. Now it always says ERROR XAMPP is already running. So it runs all the time (since I've found no means to turn it off). Is that OK? How about apache and mysql, whatever they are? Do they run all the time? I can't turn them off since the control panel is blocked by XAMPP.
Yes, it runs in the background all the time, if you've made it so it starts when you boot up your computer. You most certinaly *can* turn it off. You just open the control panel for it and hit the "Stop" buttons for each module. Localhost will not run without Apache. MySQL will not run without Apache.
And your control panel for XAMPP is in your status bar on your computer - you don't do it through the compiter's control panel. Look for it. You'll see the icon.
6) When I finally get this all sorted out, is there an easy way to put all this stuff on a USB stick, i.e., could I just copy everything over to it and maybe change a couple directory references or something, or would I have to spend another week redoing everything?
I don't know about that - someone better may be able to answer that.
But your original question was that you just wanted to show this old classmate the website. I would assume you had done all of this on your laptop so you could just take it to him and show him the site.
If you want him to actually have *interactivity* with the site (something you didn't mention before) - without an internet connection, your looking at a TON of work to allow him to post to the site. Is it really worth that to you?
Showing him the site, and giving him free access to it are two very different things. There's good suggestions up there to show him the site, but none of them will give him full access to the actual thing. If that's what you're actually looking to do, then you need to petition the home he's at to get internet access. Alternatively, see if there's something close by that already has wireless access that he could hook into (it would have to be close) and get him a laptop with wireless capabilities.