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.

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.

not sure what you mean by ‘come together’… for users there would a ‘front end’ user interface, either a website or an application that includes access control and forms and fields, etc. on the ‘back end’ there would be an application server somewhere that connects to the database and lets certain users view/edit certain things as scripted.

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.

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.

ELI5: a database is the “memory” of a program.

Every piece of data that any software uses almost certainly comes from and goes to multiple databases.

Once the data is stored, you can execute “queries” to have powerful access to update many records at a time, read particular records based on their relationship to other records, and so much more.

Your bank balances, your purchase history, your emails, every part of your digital life is almost certainly spread across a constellation of databases.

Bonus Fediverse content:

Lemmy itself uses the Postgres database extensively. Posts, users, comments, votes and more are all individually stored in the database.

Mastodon also uses Postgres. If a post goes up on Lemmy, and a Mastodon server is federated with it, the Lemmy server will send out a HTTP request to the Mastodon server containing the contents of the post. The Mastodon server will use this information to write its own record of the post in its own database.

Regarding your question about VMs: You can run a database inside a VM, or give the VM access to an outside database via queries, or both! You might run SQLlite (a small and excellent embedded database) on the VM to track its local state, while also running queries against a large postgres database to synchronize with other services in the cluster.

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.

I don’t think many businesses use MySQL when they can use PostgreSQL. Oracle is used very often. MSSQL in stupid cases.

You obviously need databases to, eh, store data, index it, process it, access it.

Also, as others say, it’s a wide concept. A file system is a database. In some sense BitTorrent DHT is a database.