There are more carbon compounds than there are compounds of all other elements combined. The study of carbon compounds, both natural and synthetic, is called organic chemistry. Plastics, foods, textiles, and many other common substances contain carbon.
In a nutshell, Google Backup and Sync is a combination of Google Drive and Google Photos. There is no need to use two separate apps, as you can do it all with a single tool. Though, it is missing an easy way to restore the backup.
For Google Drive to synchronize files between the user's computer and Google Drive storage, the Google Drive 'client' software must be running on the user's computer. The client communicates with Google Drive to cause updates on one side to be propagated to the other so they both normally contain the same data.