#platform is an overloaded buzzword. To disambiguate this term, I've broken down 3 uses of "Platform" with a quoted definition and examples.
Platform as a Business Model (Marketplace)
"A platform is a business model that creates value by facilitating exchanges between two or more interdependent groups, usually consumers and producers." -Alex Moazed, Platform Business Model
Typical business models have considered the linear downstream approach of producing goods or services to consumers. The platform business model is where a two-sided market creates an exchange between two or more groups. Airbnb is a platform for hosts and guests. Lyft is a platform for drivers and passengers. Amazon is a platform for buying and selling common goods.
Platform as a Service (PaaS)
"Platform as a service (PaaS) is a complete development and deployment environment in the cloud, with resources that enable you to deliver everything from simple cloud-based apps to sophisticated, cloud-enabled enterprise applications." -Microsoft Azure, What is PaaS?
Unlike the platform business model companies, PaaS companies have a linear relationship of providing service to users hosting their applications on their platforms. Some examples are Heroku or OpenShift.
Platform as a Product
"The use of the word "platform" is defined as a set of technologies that enable products to share data and experiences with one another." -Wyatt Jenkins, Making the Shift to Platform Product Management
A Platform as a Product typically starts internal and proprietary to a company that provides a set of capabilities. A platform could provide the capability of managing paid subscriptions, content recommendations, or search. Stripe as a Software as a Service (SaaS) company act as a payment processing platform in offering this capability to its customers.