By convention, direction of the current arrow corresponds to the direction positive charges move (or would move if they could). In metal wires, positive protons don’t move—current is carried only by negative electrons. Even though only negative electrons move, we still point the current arrow the way positive charge would move, opposite direction of the electrons. This convention started way back when Ben Franklin gave electric charges the names $+$ and $-$, many years before the discovery of the electron.
Veterans: Some military electronic training programs (for example the U.S. Navy NEETS program in the 1960s) use the opposite convention, defining current to flow in the direction of electron motion, but we don’t use that here at Spinning Numbers. We follow the SI convention for current direction.
Created by Willy McAllister.
This is an updated version of the same video on Khan Academy. Thomson is now spelled without a “p” and the video has been shortened.