The definition of open-ended gameplay.
And it was worth it. Even though Darklands lacked much in the way of pretty animations and sprites(most of the game is presented on static hand-painted choice screens), the game's world was really engrossing. From the huge amount of quests you are able to do, to the insanely large map of medieval Germany(with thousands of cities), to the intuitive pseudo-real time combat system(you can pause and unpause with the spacebar, to give orders to your party. Which inspired games like Baldur's Gate and KotOR), Darklands truly is an open-ended world.
Heck, even the very detailed manual was a delight to read(for me, at least) and I spent hours reading about Raubritters, different types of armour, The Crusades, the economy of medieval Germany and so on. While a lot of it was useless in a gaming perspective, it shows how much research Microprose did in making the game(and the manual :P).
Even when you finish the main quest(which you can choose not to), the game doesn't end, and you can still explore the open world to gain fame and glory to your heart's content.