Any company's success is a measure of the value they create for their customers. That's how Stewart Butterfield recently put it in Lenny's podcast on Product Management. Steve jobs said it famously with: Customers vote with their wallets. If you make a good enough product - they buy it. If you don't, well they don't.
Simple as that.

As a founder the single job you have is create enough value for your customers that they'd like to pay for what you have. If you can't do that, too bad. No money. Sounds simple, but not so much. The hard part about it is the value is similar to the famous utility curve. Effort on one axis, value on the other. If you do everything right, the more effort you put in, the more value. But that assumes to you listen to customers, buy what they need (not necessarily want), and provide a better experience than everyone else. When customers finally pay you, you have to keep doing this as every single competitor will try and copy you, the moment they see you create something magical or neat.


That's it. That's what it means to run a business.