Databases and their real world use examples - eviltoast

I am very curious as to how databases are used in the real world, whether you’re using MySQL and what not, how does it all come together in a real world business? Banking and gaming I know, but is it something that gets stored on data centres and then put into a VM?

I might be overcomplexing this but I understand the good use cases with VMs and containers etc just not with databases.

I’d google, but I’d like a ELI5 due to my smooth brain with these concepts, thank you.