Answer:
The main idea that is not stated in the text.
Step-by-step explanation:
As it is implied, it is not explicitly stated- you have to use inference. For example:
John was at the bus stop. He continuosly peeked his head at the timetable; checking every second to see if the bus was making its way round the corner.
Main idea- John is waiting for the bus
Implied main idea- John was getting impatient and needed the bus to come now.