Google Drive on Mac vs Google Drive online

I used to use Google backup and Sync. It worked great. I used it as a backup and knew that my files were backed up elsewhere - and even if I removed something on my computer, I had the sidebar google to auto-sync some of the files.

Now, Google has changed everything and what used to auto-sync from my computer to online, does not. Google only responds with more questions (when they respond at all) and I still do not know how to use my online as a backup and auto-sync only some of the files on my Mac.

I know this is a google question, so I apologize if this is not the place to ask my Mac-related google question.

Thanks!