The meaning of platform has evolved considerably over the years...
“A platform is a set of common components, assembly methods or technologies that serve as building blocks for a portfolio of products or services. Platforms leverage modularity to create a diverse set of derivative offerings more quickly and cheaply than if they were stand-alone items.” Automobile manufactures frequently leverage the platforms to be able to offer various car models in a cost-effective way.
Sawhney, M., Wolcott, R. C., & Arroniz, I. (2006). The 12 different ways for companies to innovate. MIT Sloan management review, 47(3), 75-81.
“Products and services that bring together groups of users in two-sided networks are platforms. They provide infrastructure and rules that facilitate the two groups’ transactions and can take many guises.” eBay is an example of a platform business.
Eisenmann, T., Parker, G., & Van Alstyne, M. W. (2006). Strategies for two-sided markets. Harvard business review, 84(10), 92.
See also Platform Business Model explained…in under 100 words.