Simon's Quest takes place in a non-linear world, so you can (and have to, for that matter) go back to previous areas at any point in the game. There are certain areas which are blocked off until you find an appropriate item, however much of the world can be explored right from the beginning. Despite the non-linear layout, the plot progression is fairly linear. There are five mansions that must be explored before you can enter the last area, and while you can skip a few of the mansions and come back later, there is no real reason to do so.
While the game does not have explicitly defined chapters or stages, it can be logically broken up into six sections; one for each of the mansions.
You start the game in the Town of Jova, with nothing but your Leather Whip 
and 50 hearts.