Am I just too old for HN now? I can understand calling something that holds your data and makes it so you don't have to do JOINs a database. I can understand

Am I just too old for HN now? I can understand calling something that holds your data and makes it so you don't have to do JOINs a database. I can understand calling something that holds your data and does JOINs for you a database. I'm having trouble calling something that holds my data and makes it so I have to "JOIN in my application" anything but a file system.