All marketplaces are platforms. Hence, Clarity is a marketplace and a platform.

A platform can be defined as a place of interaction where users with freedom of decision making power interact with each other, and the platform owner defines the rules of conduct and governance.

On the flip side, not all platforms need to have marketplaces operating on it. As an example, Microsoft developed its Windows operating system for 2 decades as a platform without a marketplace. It was a platform because app developers created many software applications for Windows OS users to install and use. It wasn't a marketplace because Microsoft didn't operate any kind of a medium for app developers and users to meet and transact with each other.

Compared to Windows OS, Apple's iOS is a platform with a marketplace built on top: app developers and OS users meet on App Store to interact and transact.