A gallery around a table top is either useful or decorative, and the difference is a couple of decisions about how it is made and how high it stands.
Screwed onto the surface of the top, a gallery is decorative. It has no real strength - a book pushed against it works the screws loose over time - and it leaves a raised edge on the top that traps dust along its whole length.
This one is jointed into the top instead. The rail is tenoned down into the top itself and into the corner blocks at each return, so a push against it is carried into the structure rather than into a screw thread, and the joint line sits flush with the surface so nothing collects along it.
Its height is chosen from what a side table actually holds. Tall enough to stop a paperback or a phone sliding off the back edge; low enough that a lamp base still sits inside it and the top can be wiped in one pass.
And it stops at the front. A gallery that ran all the way round would turn a useful table into a tray.