Proxmox VE is based on Debian. This is why the install disk images (ISO files) provided by Proxmox include a complete Debian system as well as all necessary Proxmox VE packages.
See the support table in the FAQ ??? for the relationship between Proxmox VE releases and Debian releases.
The installer will guide you through the setup, allowing you to partition the local disk(s), apply basic system configurations (for example, timezone, language, network) and install all required packages. This process should not take more than a few minutes. Installing with the provided ISO is the recommended method for new and existing users.
Alternatively, Proxmox VE can be installed on top of an existing Debian system. This option is only recommended for advanced users because detailed knowledge about Proxmox VE is required.