A Startup Is Designed to Grow Fast
A startup is a company designed to grow fast. That's the whole definition. Being newly founded doesn't make a company a startup. Neither does technology, venture funding, or an exit plan. The only essential thing is growth. Everything else we associate with startups follows from it.
This means most new businesses are not startups, and that's fine. A new restaurant or consultancy can be a great business. It just isn't playing the same game, and mixing up the two games leads to bad decisions in both.
If you want to start one, PG's point is that you need to understand growth itself, because understanding growth is what starting a startup consists of.
“A startup is a company designed to grow fast.”
Key idea
Startup = a company designed to grow fast. Not new, not tech, not funded: fast-growing. Everything else about startups is downstream of this.