Automatic Backups of data for IOS devices.

I think I have a misunderstanding and I need to get an answer either way.

I was backing up my IOS data to my iMAC. I thought that because I had sync this iPad over wi-fi checked off, that I would get a backup automatically. Unfortunately, I think I was wrong as I had to restore my iPad Air and the backup was quite old because I connect my iPad to my computer often.

So, my question is really simple...does the Automatic Backup of my IOS devices only work when you back up to iCloud as opposed to iTunes (my iMAC)?

Thanks in advance.