A Garcia comes with built-in processors that can manage IO, do precise motion control, and run simple programs, but other than that it is basically "brainless".  To get real processing power for your robot, you must connect it to a host computer.

A typical host is a powerful computer with a rich programming environment such as C++, Java, or HTTP.  You can think of the host as the brain of the Garcia robot.  It is the intellect that manages the low-level functions that are built into the robot.

The host computer communicates with the Garcia through the Garcia API (Applications Programming Interface).  This API is a software object that manages threads for robot control and communication.  It constantly monitors the status of the link between itself and the robot by using a "heartbeat" protocol.  The API can also record all communication between the host and robot to a file.  In addition, the API handles a queue of behaviors or tasks that the robot is to perform.  When behaviors get queued, the API executes them one at a time.