First things first: the only stupid question is the one you
don't ask--so none of these are stupid :)
Okay, RSS Feed. On a self-hosted wordpress blog your feed is
most likely "yourdomain.com/feed" fairly straightforward.
The RSS feed is how folks can subscribe to your blog using a
feed reader (like Google Reader) or email (if you have that side
set up). It means that whenever you post, they get notified without
having to constantly check your site.
As someone who reads almost exclusively through a feed reader
(it's the only reasonable way to keep up with the 200+ blogs I
follow) I highly suggest you make this available to your readers.
Using the Feedburner plugin makes it very simple.
And speaking of plugins. On your dashboard you want to go to the
Plugins tab on the left side of the dashboard and click on Add New.
Then you can search for the name or keyword of the plugin you want,
click to install it and then activate it.
Some will have features you have to set up (and will tell you
that once you activate it), others will just work automatically.
(The other way involves uploading the plugin files via FTP, but
this is only necessary if the plugin hasn't been added to the vast
amount of approved plugins already available.)
To find out/track how many followers you have, I suggest using
Google Analytics. There are loads of tutorials about it (including
a recent one on SITS if I'm not mistaken) out there.
Good luck!