Selvage, Tab, Label - What Is The Difference?

Before those names can be tossed around, there must be agreement about the format of the underlying stamps. There are many different formats in which stamp(s) (postally or fiscally valued) are issued and varies by country as well.

For example, discussing "tabs" goes in one direction with certain Israel issues and a different direction with USA booklet panes. Same divergence can occur when discussing gutters which for example can be formed from margin selvage, tabs or labels including combinations of some or all.

The fact is, given all of the various types, shapes and locations of "leftover" paper from the individual pane (post office issued/sold portion of a printing sheet) or issued entire press sheet, philately does not have names for all different "leftover" paper.

This recent USA issue https://goscf.com/t/79042 includes design elements in the non-stamp paper portion of the pane which are designed to be added to the actual stamps when used to pay postage and not regarded as an unapproved covering of a postage stamp which would invalidate the stamp such as tape, stickers or even other stamps would due to the fact a prior cancellation could be obscured to allow reuse or prevent cancellation now allowing for reuse later.