"Big five" publishers
The “Big Five” publishers—the publishing companies that have the most money and are the most likely to provide you with immediate compensation (if you are chosen)—include Penguin Random House, Macmillan, HarperCollins, Hachette, and Simon & Shuster. In order to have your book taken up by one of these enormous companies, you have one of two options: you can add your manuscript to a “slush pile” of thousands of other manuscripts that might be looked at by an underling and then never looked at again, or you can find an agent. The former very rarely results in publication of any sort; the latter will yield some success, but it takes perseverance.
The main benefit to publishing with one of these companies is, as mentioned above, the financial gain that could come with being one of the lucky few who get chosen. In order to get chosen, you have to embark upon the arduous process of finding the right agent. This usually involves searching through an online database of agents or networking at conferences. To contact an agent, you should send a query letter that is tailored to the specific agent and contains enough information about your book so the agent can decide whether he or she can represent you. Sometimes, you will become lucky and snag an agent quickly; however, you could wind up sending a hundred or more query letters before an agent finally contacts you.
This brings me to the primary drawback of trying to get published with one of the “Big Five”: an agent typically will represent you only if he or she thinks that your book is marketable.1,2,3 Since agents only make money after they sell a book (or at least they should—be aware of agents who ask for money upfront; they should never do that), it would not be in their best interest to waste time on a wonderfully written book that will not appeal to a large audience. If your book is very specific in nature or is a challenging read, you may be better off with one of the next two options.2