The word insight has several different meanings, but in the context of creative thinking it means an idea that appears in the mind as if from nowhere, with no immediately preceding conscious thought or effort. It’s the proverbial ‘Aha!’ or ‘Eureka!’ moment, when an idea pops into your mind out of the blue.
There are many accounts of creative breakthroughs made through insight, from Archimedes in the bath tub onwards. All of them follow the same basic pattern:
Working hard to solve a problem.
Getting stuck and/or taking a break.
A flash of insight bringing the solution to the problem.