Welcome and I'll take my stab at it. I spent the first five years of writing pulling my hair out - it's all gone now - and I was SOOOOO Frustrated about the different Story Theorists leaking their opinions and I thought they were debating, but soon I found, they are not debating, they are just using DIFFERENT TERMS for the same thing.
Of course, the net wasn't around, so there was no one "place" to congregate and discuss these things.
Many of these terms are cross-platform, so you're going to really get into issues when you start looking at transmedia - OMG!!!!!
Let's stay with Writing (Books, Novels, etc.) and with Screenwriting (Scriptwriting, Feature Film, etc.).
In the book world, the short description of your book, usually written in one line, is called a storyline and/or logline or hook.
In the screenwriting world, this is called a LOGLINE because in the ancient days of screenwriting, when there was only paper and no electronic documentation, someone at the big film studios kept a HUGE book, most likely a binder, and when people submitted story ideas, this person "LOGGED" the ideas in this book/binder. That's why in movies, they are called LOGLINES.
I work in the book world and in the movie world, to ease changing the terms, I just accept the term LOGLINE.
This is my personal preference, others who do not WRITE scripts may find this offensive or unsound or unfit. It works in my system.
Above, I see someone called the logline "the tagline," and I'm going to fight tooth and nail about this cause in movies, the tagline is the short term used to "hook" readers.
For example, a movie title can be Lover's Lane and on the movie poster, the tagline might read Love comes in two flavors, blood and beauty. That's a tagline, it's a catchy phrase that's often written on movie posters and stem from the marketing department promoting movies to the target audience.
Now that's the ONE LINE DESCRIPTION.
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When you get into longer descriptions, we're going to encounter several issues, debates, and paradigms.
For some reason, people can agree on mathematics to send ships to the moon, but writers will NEVER AGREE on these terms - go figure....
Keep in mind, most of these terms are driven by the ancient and antiquated system of book publishing and many writers view "defining their own terms" as some sort of defiance to the system, but I always thought the purpose of writing was communication not confusion....
Usually, the back of a book or the book cover description is often described as a Synopsis (this is in Marketing).
(In the Writer's Life) when you are submitting documents to a publisher and/or agent, you are asked to submit a Summary or a Synopsis, and the difference between these terms is the LENGTH.
Some agents think the synopsis is 1-3 paragraphs, others think it is 1-2 pages.
Same goes for the Synopsis.
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My advice in getting complete clarification is to first ask - who is asking for this?
If this is YOURSELF and you're writing, use your own terms that make sense to you.
The terms will change according to the industry, the purpose, the target audience, and the situation.
I would STRONGLY SUGGEST again, find out who is the description for and ask them to provide you with their list of terms or glossary or go to their website and read this information.
I know this is a lengthy post, but this post requires more in-depth information and you should know what's going on and I hope this helps.
Just my ten cents.
