It sort of depends what you mean by 'install'.

Most of the data about a concrete5 site is stored in the database, it's only the files you upload to the file manager (and a few config files) that are stored within the folders of your install.

So if you try to re-install concrete5 to the same database, it will complain and say that there's already tables and data in there - you can only install concrete5 to a blank database. So there's a bit of protection there.

In terms of the files, you wouldn't want to just dump a new copy of concrete5 over the top, that's going to create a mess I think.

If you are talking about one the auto-installers, like Softaculous, I'm actually not sure what would happen there, as I don't personally use those methods of install. I reckon it would complain that you've already installed concrete5 though.

If you are wanting to reinstall, my suggestion is that you simply take a full backup of the database and the files. Then delete the database (or create a new one) and remove or shift the files out the way. Then you can reinstall, but you've got the backups _just in case you need them..._