Making the transition from scribbler-of-entertaining-prose to aspiring-to-be-published-author can be tricky. And sometimes it seems that the technical details of that process get glossed over, so I thought I'd, ya know... start at the beginning (and when I come to end, stop.)
And when I say "the beginning," of course, I'm referring to the marketing process. Which means you've already got a shiny, edited and complete manuscript ready for publication.
First, you should know exactly what you are asking for from the agents you query. You are not asking them to publish your novel. You are not even technically asking them to sell your novel. You are asking them to represent your interests in the sale of the publication rights (more on that later). Your agent contacts editors on your behalf and, if offers are received, presents them to you so you can decide whether or not to accept (like a real estate agent would). They will also offer their expert opinion regarding that decision and negotiate the details of your contract.
Therefore, when you query an agent, you should state you are seeking representation (not publication).
Which brings us to publication... Naturally, you are hoping for a sale, but what exactly are you selling?
You are not selling your novel. You are not selling the copyright to your novel. What you are selling, for the most part, are the rights to first publication (and sometimes other rights we'll discuss in a moment).
So what are first publication rights, anyway? Well, that means simply the right to publish a book which has never been published before. This is particularly important for newbie writers to understand in this age of POD publishing options.
Sites like Lulu.com, CafePress, and CreateSpace offer writers the ability to have their book "in print" immediately, but many writers may not realize that by using their POD publishing services, they no longer have rights of first publication to offer to a traditional publisher. Also, publishers vary in their opinion of how much content may be published online before a book considered "published," so it's wise to limit how much of your manuscript is available on your website or blog.
Publishers are far less interested in purchasing the rights to reprint a book, so if your goal is a traditional publishing contract, don't put yourself in a situation where you have no first publication rights to offer.
Finally, in addition to the rights of publication, your contract may also include additional rights... such as rights to electronic publication or rights to publish in another language. Or it may include options for these rights, like they may require a chance to counter-offer on a foreign deal, etc.
In the end, the right to your book remains with you.