A clean installation will clean the partition, and provide a fresh installation on the system.
Installation (or setup) of a computer program (including device drivers and plugins), is the act of making the program ready for execution. Installation refers to the particular configuration of a software or hardware with a view to making it usable with the computer. A soft or digital copy of the piece of software (program) is needed to install it. There are different processes of installing a piece of software (program). Because the process varies for each program and each computer, programs (including operating systems) often come with an installer, a specialised program responsible for doing whatever is needed (see below) for the installation. Installation may be part of a larger software deployment process.
Installation typically involves code (program) being copied/generated from the installation files to new files on the local computer for easier access by the operating system, creating necessary directories, registering environment variables, providing separate program for un-installation etc. Because code is generally copied/generated in multiple locations, uninstallation usually involves more than just erasing the program folder. For example, registry files and other system code may need to be modified or deleted for a complete uninstallation.