Well, we're here.
To the post I don't really know how to write -- not because I don't get it, but because there are so many ways to go with this. Anyway, I'll just do my best, and assume that you've written a novel which you want to get published.
It really just depends on what you want to happen with this book. If you're only wanting to share it with family and friends, then self-publishing might be a way to go. Or maybe you're like me. Maybe you're looking to launch a career with this novel, start building a name for yourself.
Since I am trying to publish with the traditional route, I'm not sure I know enough about the process of self-publishing to explain it to other people -- so you're on your own, pal. (In this stage of your life, Google will become your best friend, if it isn't already.) Just look it up and check out some other writing websites and blogs.
But back to that traditional publishing idea. Technically, you don't have to have a literary agent, but it makes things a lot easier on you. A lot of publishers won't look at work unless it's represented by an agent; then you'll just end up in the slush pile, and you'll be lucky if anyone ever checks out your book. But what an agent actually does for her/his clients actually goes much deeper than that -- here's an explanation by literary agent Nathan Bransford:
So really, you just need to decide what direction you're wanting to go in with your book, and explore your options from there.