Trello provides a simple [RESTful][1] web API where each type of resource (e.g. a card, a board, or a member) has a URI that you can interact with.
For example, if you'd like to use the API to get information about the [Trello Development board][2], you'd use the following URI:
https://api.trello.com/1/boards/4d5ea62fd76aa1136000000c