"Bookmarks Toolbar Items" is a stretchy (expand/shrink to fit) control that shows bookmarks from the list in the Bookmarks Toolbar category.

I realize that's a little confusing, because Bookmarks Toolbar is a piece of physical real estate in the toolbar area AND it is a category of bookmarks which you can display on a different bar by moving the "Bookmarks Toolbar Items". Maybe it would be better if they have different names, but there you have it.

Here's a screenshot for context if it's helpful.

thanks jscher2000, Just seems to complicate things for me. Means you can show an empty toolbar instead of hiding it.

Some people like to move their Bookmarks Toolbar Items to unusual locations like the Menu Bar (if they turn on the menu bar) or the Tabs bar (if they only open a few tabs per window, I guess). But, the standard way is fine with me.