They seem pretty much the same at first glance, and the differences seem slight, but they are not. Both perform similar functions in terms of data storage and both are in the cloud, but they are very dissimilar in many ways. Google Drive users are being encouraged to switch to Drive for Desktop as the old Google Drive will no longer be provided with Backup and Sync.
Google Drive: Setting up a Google account allows access to all Google services, including Drive, Gmail, Photos, Docs, Sheets, Slides, Forms and Keep. It is a manageable platform for personal use and very small businesses as the storage capacity is only 15GB. In effect, the storage capabilities operate much the same as a computer's hard drive, but any documents, photos, audio, and video files are stored in the cloud on Google's servers rather than locally.
Google Cloud: The full name is Google Cloud Storage (GCS), which stores its customers data online, specifically in the Google Cloud Platform (GCP). which provides much stronger Cybersecurity than Google Drive for storing backups as well as much more storage space.
Customers of both of these applications are advised to either upgrade to Google Workspace or make other plans as many of both platforms' features are being discontinued in favor of the new all-inclusive platform.