The model comes from Team Topologies by Matthew Skelton and Manuel Pais: stream-aligned teams own a flow of value to the customer, platform teams reduce their cognitive load, enabling teams help other teams learn something new, and complicated-subsystem teams own what needs deep specialist knowledge. A platform team is measured by how little the other teams have to think about the platform — not by how much it can do.
The trap is building the platform you would want yourself. Platform teams are often the most senior engineers in the organisation, but the customer is the developer who wants to deploy their service before lunch. More in Platform as a product and in Sluta skriva wiki-sidor, börja bygga golden paths (in Swedish).