Before beginning the search for treasure, the player first creates a customizable avatar. This avatar is much like that of FarmVille's avatar series. There are many islands to travel to for treasure. You can also customize your own island, such as add furniture like chairs, huts, plants and even expand the size of the island, similar to the farm space on FarmVille.
Like other games on Facebook, It is a great benefit to have "Neighbors" who can send you gifts. On many of the higher level islands, you must open gates which require certain colored gems (blue, purple, green, orange, red) to open, which you can only get from (currently one) a tree on your own island (but this is only one random colored tree), through random events from digging (receive only a single random gem, but you can share the gems you find with friends), or by requesting friends to send you some.
On each island, there are a certain amount of "Treasures" which contain objects that make up collections. When a collection is completed, the player will receive a reward in the form of money.
Source: Wikipedia, "Treasure Isle (video game)", available under the CC-BY-SA License.