GardenBot is a garden monitoring system. This means that you put sensors (temp, humidity, moisture, light) in your garden, and GardenBot will show you charts of the conditions in your garden -- so you can see the world the way your plants see it.
GardenBot is also essentially a test-bed (sandbox, etc.) for playing with different kinds of sensors and exploring the various challenges in implementing a garden automation system. And since each part is designed as a module, it is relatively easy to expand the system.