Whazzat you say?
Wikipedia's link above gives an excellent rundown of the definition.
I'll save you some trouble of reading all of it. Since we are new novelists here, we have the option of:
1. Self-publishing: A good option for self-publishing is Lulu.com.
Don't be put off by their corporate title, they're really good with the services they offer, and ease of use, I've used them in the past to put together a book of short stories called Learning the Game, available on Amazon. No Lulu is not free, but you can pick what you need to get your print on demand book out for less than 30 bucks. That's if you do some or all of the work yourself: mainly developmental editing, line editing, proof reading, cover design, copywriting, and book design for hard copy and the various ebook options. And of course, distribution and marketing. And ISBN,
2. Vanity press publishing. These are publishing outfits that will take your novel and publish it with little or no effort on their part, and charge you a bundle for it. Usually no help on marketing. Vanity presses might have been a good option back in the day before self-publishing, hybrid publishing, print on demand, and ebooks became available. For memoirs and the like, with pictures, it may still be useful for the well-off. Vanity presses have had a bad rep because of some scammers. Many vanity presses will not look at you if you want to publish ebooks. These are my views/biases without ever having gone this route.
3. Traditional publishing,
For us of a certain age, most of what we've read are novels that have been traditionally published, often by one of the big five publishing conglomerates based in NYC.
One of the granddaddies is Knopf who's published one of my favorite novelists, John Updike. I've had the privilege of being rejected by one of their senior editors, "because my characters didn't grab" her. I met her at the excellent Lake Tahoe Community of Writers conference. Usually we mere mortals cannot submit to, or converse with traditional publishers without them having first been convinced by an agent that a novel is worth considering. Agents are the narrow neck of the bottle, necessary for contact with one of the major publishers, Of course there are many smaller publishing companies that may look at your submitted novel, sometimes even without an agent.
But having had an agent, who couldn't convince a publisher to take my novel, I look at it this way. There are now well over 100 MFA programs in the United States turning out I'll guess about 20 graduates each year, Many of these programs have been in business for (let's guess) 20 years. That's 20 x 100 x 20 = up to 40,000 potential writers hitting up agents and publishers over the past two decades, not counting newby authors who aren't products of writing programs, as well as already published authors. Probably an underestimate. Statista says that recently about 50,000 (not necessarily new) works of fiction are published in the US each year. Therefore the competition for agents is fierce. And agents can only convince x publishers to accept the novels that they're peddling. The number for x depends on the quality of the agents involved, and at best is probably less than 15%. So the odds of you getting an agent for your new novel is slim, and a landing a publisher, slimmer still, though I know the writing magazines are full of first time writers describing their route to publication. Skill, timing, topic, relevance, personal contacts, persistence, and a huge amount of luck seem to be the elements that count. Then there's more bad news. First time novels tend not to sell, for example Jonathan Franzen. A recent exception is Where the Crawdads Sing. I know I'm sounding victimy, but I accept that my novel rejected by 20 publishers was just not good enough, so I've spent another few years learning some more, and writing some of some more novels.
4. Hybrid publishing, Check out the Wikipedia link above. It's good but they underestimate the critical valuable element of many of the better hybrid publishers. Think CURATED. Unlike companies that help you with your self-publishing (Lulu), and vanity presses, the better hybrid publishers accept (so they tell me) about 5 out of 100 submitted manuscripts to work with. This filters out (and I say this with love) the manuscripts of lesser quality. At writing conferences, I've heard serious folks in the biz say that hybrid publishing is the future of the publishing industry. One of the best and oldest is Greenleaf. I've chosen to sign up with Wheatmark because I like their personal touch, expertise, and flexibility. I can also continue to query agents, and if I snag one, Wheatmark will charge me only for work completed, and then I am free to skip down the publishing path hand in hand with my new agent. I've received great developmental edits from Wheatmark, and I'm waiting for my line-edited ms to come back in a few days. They designed a great cover even though I liked my own (see earlier post, Book Cover). I accepted theirs when all of my beta judges, including my senior project manager at Wheatmark, with years in the business, preferred theirs to mine. Another lesson for us newbies--accept good advice from professionals in the book business. More on this later. And I promised you some up front costs of publishing Baby Doe. Okay, later on that too,