It can be used to develop stand-alone interactive objects or can be connected to software on your computer (e.g. Flash, Processing, MaxMSP).
The open-source IDE can be downloaded for free (currently for Mac OS X, Windows, and Linux).
Sensor Shield allows you to connect to various modules like sensors, servos, relays, buttons, potentiometers.
Each functional module has buckled port with VCC, GND and Output, which has corresponding port on the Sensor Shield, connected with a plain 2.54mm dual-female cable you may start playing already.
Buckled brick cables are like cement for bricks, make the connections easier, secure and more professional looking.