You use it to snag attention for your book or story or screenplay or, if you write the logline before you start working, you use it to focus your mind on the heart of your story so you don't go wandering off on interesting side paths and lose your way to the end.
Here's another use I've just discovered: Now, after it's published, I'm told people don't like the title of EEL'S REVERENCE. The want to call it ELL'S REVERENCE. Their minds slide right off the word EEL. Then, when they see the word is EEL, they're all, "Ewwww! Eels!"
So I've had to develop a log line or tag line or whatever you want to call it: "The Eel is a place. The reverence is ... complicated."
My hope is that deconstructing the title like that will show people that the title is appropriate AND that it isn't about squiggly things. Well, some of the characters are fairly squiggly, but....
Here is a good article about developing loglines. Here is another one. Although these articles are about scripts, I recommend coming up with loglines for your books and stories. You can use them in conversation, use them in your email signature, use them on bookmarks, postcards, business cards and in ads. Remember, they're useful when you need to:
- tell someone what your story is about
- focus your mind on the main story arc
- snag attention and interest for your work
- justify your title