As indicated, it's just a place where the downloaded rpms are stored before/during patching. After patching, you can always delete them, just make sure you're not patching at the time. Don't worry if they are ever needed again for any reason, your update processes will download them again for you. This would happen if, for example, you ran a command to force a reinstall of a package or set of packages.
We are the people our parents warned us about --Jimmy Buffett