Computing without databases is like going into a grocery store and all of the items are in one great pile. Sure, given enough time (CPU) and resources (RAM) you could find what you’re looking for, but it’s horribly inefficient.

Instead, things which are similar are grouped together, like the baking aisle (tables) and if you have to get most of the items for a cake, you know it’s on a specific shelf.

ELI5 due to my smooth brain with these concepts

Database is a broad term, nearly any computer system that stores structured data like lists of names or transactions has a database of some kind. Dedicated database platforms like MySQL just make it more efficient / faster / easier to query and store data.

I think The Manga Guide to Databases would be a good read for you.

Be sure to avoid places where you can get the book for free such as here.

If I understood your question correctly,

A database is a base for your data, its where your data lives.

A data is the most important thing for most modern applications. You have an account in Lemmy. You have made posts and comments. All that post texts, images, etc has to be recorded somewhere in the server. Thats what a database does.

The Lemmy app we are using on our phones needs to download content from Lemmy so it can be displayed to us. Lemmy might just have one big file full of links, but that’s annoying to have to write code to handle. Or it might have a folder full of files where each file is a post, but that’s also a bit annoying to write code to manage.

It (probably) uses a local SQLite database to store all of the cached posts.

Conceptually, a database is just a place to store things, just like a big text file. The database just handles a lot of the grunt work for you and makes it easier to search, organize, and filter the data.

So anywhere there is data, there could be a database.