Some major disaster has happened in the future, and some how those in the future have managed to alert some people in the past by sending messages back in an attempt to prevent it. They are altering the past in very many tiny ways hoping that it will cause a chain reaction that will eventually lead to the prevention of the disaster. Everyone on the island has a part, big or small, to play in eventually stopping this disaster.

The island because of its strange magnetic field is somewhere where these future messages are focused so they can be understood, but it leads to lots of strange things happening. This was discovered by Dharma, or possibly the original Others (the Black Rock?)

To some these future messages are just images, random things like the numbers appearing. Other people can understand the messages better, such as the Others on the Island and possibly those on the List. To them they are clearer and they are attempting to stop the disaster.