A deployment is a deployment of a flow, i.e. a way to run the flow. A deployment is not something that needs to be run. For example if you want to run a deployment on kubernetes you need to create a Kubernetes cluster and then you can deploy the deployment to it.

All tasks run in the cloud get executed through a deployment. For infra, see Cloud.https://docs.prefect.io/concepts/deployments/?h=cloud#concept-deployments