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 Terry Jones, a young and indigent archeology student who decides to steal the Eye of the Condor (a Mayan jewel) from the museum where it is being held. According to a tale you heard from your uncle, bringing the Eye back to the statue of the Condor god in its Mayan temple would lead to a great fortune in gold.
You have to succesfully steal the Eye of the Condor (and also fetch another couple of items that you will need in the sequel about Terry's adventures in the Mayan temple).