As name refers in managed hosting you will get everything managed or installed on server like cpanel, Windows, email services, brute force etc. If you will get any issue then you can directly contact your provider. But in Unmanaged hosting you have to install everything according to your need. You will get physical server maintenance gurantee only.
Like in unmanaged server you have to install cpanel/WHM "https://hoststud.com/resources/installation-of-whm-cpanel-in-centos-7.993/" at your end.
The core difference between managed VPS & unmanaged VPS hosting is, As the name suggests, the managed VPS hosting provider manages server maintenance & up-gradation & is slightly cost-effective but the best option for novices. And for unmanaged VPS hosting providers, only manage the physical server & its guaranteed uptime, and it is cheaper than managed VPS Hosting but excellent for experienced users.