system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is information stored in computers and drives when theres no power?

So for example if I found a hard drive that I havent used for years and just plug it in to my computer, the files would still be there. 

How? What is physically storing that information if it's not being done with electricity. What changes if I delete the files? Theres no limit to the number of times I can change what data is being held so it cant be something physical right?

Please help I've started thinking about this and now I'm very confused.
gpt
Depends on the drive.

Old platter HDDs store information using magnetism.  Inside, there is are disks of magnetic material.  When information is stored, a small wand magnetizes/demagnetizes parts of the disk (1s and 0s).  Since magnetism doesn't need power to stay, the information is there even when the drive is unpowered.

Newer SSDs use transistors to store an electrical charge (charged/not chares is 1s and 0s).  The initial charge requires electricity, but once it is stored in the transistor, it doesn't require any additional power to stay charged - think of it like  a really tiny battery - once it is charged it stays charged until you pull the power out.

Changing/deleting files is just changing the magnetism (HDD) or transistor charge (SSD).  You can do this a lot before the drive wears out.