It's a textual adventure (some graphic embellish it, but is purely decorative and has no role in the game).
You give commands usually composed by a verb plus a noun (e.g. "go north", "examine desk", "drink potion") and are told what happens ("you cannot go in that direction", "there is a pen on the desk", "you feel reinvigorated"). You have to explore the locations, collect items, use them when appropriate and in general imagine how to overcome the various problems in order to accomplish the final goal of the adventure.
You are Nigel Stevenson, a young guy in modern times who follows the indications of a legend and finds himself in an alternative (fantasy) world. The princess of such world has been kidnapped by an evil wizard.
In the the previous adventure (La Rosa Scarlatta - parte I) you managed to find a scroll and an enchanted sword vaguely mentioned in the legend and reputed to be necessary to accomplish your task.
Now you must travel through an enchanted valley full of dangers (trolls, the last fire-breathing dragon, etc.) to reach the dungeon where the evil wizard imprisoned the princess.