With managed VPS hosting your hosting provider will be responsible for configuring your server, doing routine maintenance, keeping your environment secure, and more. The actual services included with managed VPS depend upon the hosting provider you choose.
With Semi-Managed VPS, its a mix of a unmanaged and managed service. The provider will generally provide updates to the back-end system, monitor your services, and provide some additional support, outside of what a non-managed service would.
With unmanaged VPS you’ll have a lot less hand-holding and generally be responsible for general server admin tasks, maintenance, security, and more. With unmanaged VPS hosting, you’ll need to have some technical chops to be able to run your server efficiently.