The object of the game is to buy a car and a villa in a maximum short period of time. Also, I guess, the objective is to get yourself in the hall of fame - to be recorded there you must have a rating sufficient for that. You are recorded as a hero when you press on the 'Quit' (F10) menu item. Then your current game will end.
When you get on “The Exchange” day you can make transactions in the Exchange window. To get there you must have an apartment and a car.
Here you can buy oil or land or both once a day, and bear in mind that the sum of purchase must not exceed the cost of your apartment and car (With the only exception of Ferrari 575M and Villa).
During next tradin session oil and land prices change and you can, selling the reserves that you have at your disposal, earn in differences. Unlike buying, you can sell as many times a day as you like.