What Is the difference between iCloud and iCloud drive?

iCloud includes a variety of services. One of them is iCloud Drive and another is iCloud Photos (there are also other iCloud services). If you use a computer internet browser and log into iCloud.com you can see both of those. If you are using an iPhone, iPad or iPod Touch, you access iCloud Drive via the Files app and photos via the Photos app on the device.

More information:

iCloud - Apple

and

iCloud: What is iCloud Drive?

and

Set up and use iCloud Photos - Apple Support

Think of iCloud as a filing cabinet and iCloud drive as one of the cabinet's drawers you can use to store things. It is designed to store files that don't fit in any of the other drawers.