In previous versions of Apple OS X, users would mistakenly remove items from the dock when clicking on them.
As the icon would move up a smidgen, it would suddenly and without notice pull off the dock and “poof” disappear.
Attempts were made to correct this problem by having a delay before icons would be removed from the dock completely. However, this confused users who were intentionally trying to remove icons from the dock.
Finally in OS X 10.10 Yosemite, Apple has included a label that appears for icons being moved off the dock.
After a short period of time, the word Remove will appear above the icon to indicate it will be removed if not returned to the dock (before letting go of the mouse button).
This is helpful for people who might be organizing their dock icons.