Okay, there's no official literary term I could find that starts with X so I have to cheat a little. But that's okay, because EXCERPT is an important term to understand in the publishing industry.
As in posting an EXCERPT of your work on your blog. Be careful with this one. Most of us aren't the best judges of what's good and what isn't in our own writing. We can post something we think is fabulous, and really it stinks. This makes us lose credibility and look unprofessional in an industry that demands it.
If you are under contract, don't post anything from your manuscript until you receive permission from your publisher, and then only post an approved EXCERPT.
As for posting an entire manuscript online? Again, dangerous territory. Many publishers will consider this previously published and not touch it. Although this is changing as we speak so I'm not even sure why I bring it up as it makes me look out-dated and ignorant. But hello, it used to be the case. Now, self-published e-book authors with work that sells extremely well are getting offers from agents and publishers. Think The Christmas Box and The Shack. Think Amanda Hocking and Karen McQuestion.
Self-published authors with anything that sells extremely well will get offers from agents and publishers. As they say, "Show me the money." That's what it's all about-- money. If an author, self-pubbed or whatever, is a potential money machine, then the calls will come.
But until you are a proven money-machine, be careful what you post online, and especially avoid EXCERPTS from your current works-in-progress.