Freemium
Freemium is a pricing model where the core product is free forever, and you charge for advanced features, higher usage limits, or team capabilities. Unlike a free trial, which expires, freemium gives users an indefinite free tier that doubles as a permanent acquisition channel: free users market the product, generate word-of-mouth, and form a pool you can convert later.
The trade-off a founder has to get right is the line between free and paid. Give away too little and free users never reach value, so they never become advocates or upgraders. Give away too much and you carry the cost of serving people who'll never pay. The model works best when the free tier delivers genuine value but naturally hits a wall as the user grows, more seats, more volume, more power, so upgrading feels like a reward rather than a toll. It demands strong margins, because most free users never pay.