It is in the documentation:
provides a hosted server and UI instance for running and monitoring deployed flows. Prefect Cloud includes:
• All of the features of the local Prefect UI.
• A personal account and workspace.
• API keys to sync deployments and flow runs with the Prefect Cloud API.
• A hosted Prefect database that stores flow and task run history.
See the Prefect Cloud
documentation for details about setting up accounts, workspaces, and API keys.