Players represent individual pirates, using them to gain Victory Points by amassing booty and, even more importantly, earning Notoriety for their dastardly deeds. Seizing merchants with cargo ranging from useless paper to the monumental treasure of the Mughal emperors, attacking and sacking ports, fighting storms and scurvy, seeking safe haven in infamous pirate ports such as Tortuga and Madagascar, and, hopefully, using Letters of Marque to retire successfully.
And while the player is doing this, all of the other players, at the same time, are playing their cards and seizing opportunities to stop the pirates. There is a constant interplay among players, and you never know what is going to happen when you set out to do something.