When you go fishing with a special kind of fishing line called a fly fishing line, sometimes you use something called a fly as bait instead of a worm or a fish piece. Flies are like tiny bugs that look like real ones and different types of fish like to eat different types of flies.
When people write books or stories about fly fishing, they often include information about how to make those special flies and how to tie them onto the fishing line. This is called fly tying because you use a special kind of string called fly tying thread to attach the materials onto a tiny hook.
Some books about fly fishing are also fiction stories which means they are made up stories and not true. These stories can be really exciting and fun to read even though they don't actually happen in real life. Back to the books about fly fishing, they also often have important information about fish, rivers, lakes, and other things you need to know to catch fish using a fly.
All of the books about fly fishing, whether they are fiction stories, instructions on fly tying, or information on how to catch fish, have a special list at the end called a bibliography. The bibliography is like a special page that tells you where the author got their information from so you can learn more about it too.