"Tell me something that's true, but nobody agrees with." Peter Thiel
If you don't know Peter Thiel, he along with Elon Musk (Tesla, SolarCity) and Max Levchin (Yelp) created this tiny payment processing company named PayPal. You may have heard of them. They since sold the company to eBay for $1.5 BILLION and all have gone on to start their own billion dollar companies. Peter has written a book "Zero to One" which I would recommend to everyone, not just entrepreneurs.
This one question gets some context with this statement:
"What great businesses is nobody building? In business, every moment happens only once. The next Mark Zuckerberg won’t be building a social network.”
Whether you interpret this as work in the white space or zig when they zag; it boils down to creating a service or product to disrupt you industry or in other words ALWAYS try to put your competition (and yourself) out of business.