  This is a write-up of a short tutorial talk on high-intensity QED,
video-presented at the 2021 annual Christmas meeting of the Central Laser
Facility at Rutherford-Appleton Lab, UK. The first half consists of a largely
historical introduction to (quantum) electrodynamics focussing on a few key
concepts. This well-established theory is then compared to its strong-field
generalisation when a high-intensity laser is present. Some supplementary
material and a fair amount of references have been added.
