The Keeper’s Reign is in this stage of production. I am currently querying both agents and publishers, and I have been never more excited, anxious, determined, and discouraged all at once.
With the modern job hunt as it is, you've probably turned in a resume online or even in person and then had to wait for some unspecified amount of time to hear back whether or not you're a good fit. Sometimes, you don't hear back at all. This is essentially what a query letter is. You send this email off into the ether, and you hope that one day somebody will respond. Sometimes they do, sometimes they don't and sometimes their response time is six months. Six months of waiting, of twiddling your thumbs and of praying somebody will request your full manuscript. I'm currently at this stage I'm in now.