Full explanation
Traction is the visible evidence that your startup is working. It can be paying customers, active users, organic signups, press coverage, or any metric that goes up consistently.
Investors look at traction before anything else. A demo without traction is just a slide. A demo with 200 paying customers is a business.
Building traction is harder than building the product. Most founders are surprised by this.
Concrete example
You launched 3 months ago. You now have 80 paying customers and you grow 20% every month. That is real traction.