If terms like "Kp" or "CME" mean nothing to you, this is the two-minute version of what's actually happening above your head.
The sun constantly streams charged particles out into space, called the solar wind. When those particles reach Earth, our planet's own magnetic field funnels them down toward the poles, where they collide with oxygen and nitrogen in the atmosphere and make them glow. That glow is the aurora.
Sometimes the sun erupts and hurls an enormous cloud of magnetized plasma out into space. If that cloud happens to be aimed at Earth, it slams into our magnetic field roughly a day or two later, sharply increasing the number of particles funneling toward the poles, and a much stronger, more widespread aurora.
A coronal hole is a cooler, darker patch in the Sun's outer atmosphere, called the corona, where the magnetic field opens up and lets a steady stream of fast solar wind escape continuously. Unlike a CME's single burst, these streams can affect Earth for several days, and often repeat roughly every 27 days as the sun rotates.
The Planetary K-Index (Kp) is a simple 0 to 9 scale showing how disturbed Earth's magnetic field has been recently. It updates roughly every three hours, not continuously, so think of it as the latest snapshot rather than a live reading. Lower numbers (0–2) reflect quiet, calm conditions with respect to geomagnetic activity and the aurora usually stays confined near the poles. Higher numbers, such as 5 and up, mean that a geomagnetic storm is underway, and the aurora can be seen much farther from the poles than usual. Numbers greater than 7 are typically reflective of a significant geomagnetic storm and have the potential to drive aurora into mid-latitudes.