The Wehrmacht wanted tanks and their first attempt kind of sucked. There were some good designs on the drawing board, but those would not be finished before they were needed. Thing is, Hitler was in a hurry to start his war, and for that you need weapons. German industry was asked to quickly make a larger and better Panzer I, adding what was learned from the Spanish civil war, a third crewman and a 2cm autocannon.
Despite not being the best solution either, the Panzer II they made was used everywhere and for everything; it was primarily a recon vehicle, but was also reconfigured into a Marder or a munitions carrier. Later in the war, a certain Heinrich Kniepkamp got a hold of the design and I guess he liked race cars, because he certainly did his best to turn the Panzer II into one. Also, light tanks were on the way out, to be replaced by Panthers that were eminently better suited for armoured combat. The Panzer II story ends with a bunch of spare turrets ignomously being used as fixed emplacements (or "bunkers), like on the Danish island of Fanø, guarding the former Kurhotellet.
These were the prototype versions of the Panzer II. It could protect its crew from rifle fire, but not much more. Some of these trial vehicles actually fought in Poland, Norway and France which seems totally ludicrous
Initial production version A got an armour upgrade and some new bits, but was essentially the same as the final prototype, and so was version B. This shows why we now have semantic versioning.
Model C was the definitive edition of the Panzer II. It was 99% identical to earlier models but received a mix of field upgrades over the course of the war, like bolt-on frontal armor or a model F cupola. While still a stopgap design, it did play an important role in early Blitzkrieg victories.
I have no idea what they were thinking, but these models were completely re-designed as fast pursuit vehices, like a police cruiser. As there were no televised car chases back then, it didn't work out and they were scrapped after a few months of service.
Because the Panzer II wasn't as good as it could be, they tried building a completely different vehicle using the same idea and a Schachtellaufwerk. It was crap too, and quickly discontinued.
The J model was supposed to be a recon job, but someone forgot the "sneaky" memo. It was slow, overweight and no one feared its tiny cannon. Maybe it could lumber to safety while the enemy was busy laughing...
RAL7028 DGnM
Another Panzer II-style design, this "Luchs" is considered to be cute by many a WoT-player - but it still sucked. And only a hundred were built, so it had minimal impact but cost a lot. They should just have license-built their enemies' M5 Stuart, which is a better tank in any regard.
Basically a model H with a new turret, housing a 5cm gun. Four were built, but none were used. A total waste of time and resources...
5 cm KwK 39/1