Econ mode, or Energy Saver mode, is a setting that works similar to central AC.

The room air conditioner will turn off once the set temp is reached; the fan then cycles on (for 20 sec.) every 10 min to sample the air temp. If the room temp is above the set temp, the compressor will turn back on.

Since the room air conditioner is not running at all times, this setting will help save energy while ensuring the room temperature stays at the set temperature.