2 outlets that operate independent of each other
Each outlet can be configured as NO (normally open) or NC (normally closed) depending on need.
Tool can be used to test code by the Arduino without having to use high voltage connections
NC (normally closed) outlets controlled with independent switches and can only be "HOT" when Arduino PIN is "HIGH"
NO (normally open) outlets controlled with independent switches in this mode the Arduino will stop power to the outlets when the Arduino PINS go "HIGH". You will need to play with this in order to understand it's function.
Sparkfun has a guide that should be reviewed also.