Platforms must perform three key functions in order to encourage a high volume of valuable core interactions, which we summarize as pull, facilitate, and match. The platform must pull the producers and consumers to the platform, which enables interactions among them. It must facilitate their interactions by providing them with tools and rules that make it easy for them to connect and that encourage valuable exchanges (while discouraging others). And it must match producers and consumers effectively by using information about each to connect them in ways they will find mutually rewarding.