Brand-new drives often come unformatted. You must initialize and partition them.
Setting up an external hard drive is usually a plug-and-play process, but depending on whether you are using Windows or macOS, and whether the drive is brand new, you may need to take a few extra steps. how to setup an external hard drive
If you have a drive that you want to use on both a Mac and a PC, the native formats (NTFS for Windows, APFS for Mac) won't work well together. Brand-new drives often come unformatted