Stub has a few related meanings, all involving something short or incomplete:

The most common meaning is the small part that remains after something has been used or torn off. When you use a ticket to enter a concert or board a plane, you keep the stub as proof you paid. It's the leftover piece that stays in your hand after someone tears off the main portion. A pencil worn down to a tiny nub becomes a stub barely long enough to hold. The end of a used candle is called a stub. Even tree stumps, those short remainders of cut-down trees, are related to this same idea.

To stub your toe means to jam it painfully against something hard, like a table leg or a curb. The impact hits the very end, or stub, of your toe with sudden force. Anyone who's ever stubbed their toe in the dark knows that sharp, surprising pain.

In writing or research, a stub is an incomplete article or entry that exists but needs more information. Articles marked as stubs are started but not finished, waiting for someone to add details. It's like turning in an outline instead of a complete essay: the basic structure is there, but the substance is missing.