A proxy server acts as a gateway between you and the Internet, verifies and forwards the requests that you as a client make to other servers on the Internet, placing here a backup point that allows you to apply security controls when browsing the web. These devices are commonly located in the organization's own infrastructure, requiring dedicated equipment for this purpose.
A Proxy Cloud is cloud-based rather than requiring dedicated on-premise hardware in a corporate datacenter. Internet traffic flows through the cloud proxy acting as an intermediary, separating end users from the websites they browse and the applications they use. Proxy servers offer various levels of functionality, security, and privacy, depending on the use case, needs, or company policy. And, compared to other forms of inspection, the cloud proxy offers control over the user, internet, corporate applications (O365, GSuite, etc.), non-corporate applications, internal applications and information leakage. The fact that it is in the cloud makes it even easier to use from remote locations or even home offices, not being necessary to have traditional vpn access to use traditional on-premise proxy and taking security outside the perimeter.