Why I'm getting four hard drives?
Your internal SSD is formatted to APFS. This means your SSD contains two partitions in the default partition scheme:


EFI
APFS container


The APFS container itself contains four logical drives (volumes) - some of them with a specific role:


Preboot
Macintosh HD (your main volume with the system files and your data/apps)
Recovery (recovery system)
VM (virtual memory)


In the default scheme the four volumes share the whole space of the container - the reason why all show 250.79 GB in your screenshot.

In fact each volume is smaller but may be expanded dynamically.

You can get their real sizes by entering diskutil ap list in Terminal.app.



At least three of the four volumes are required to boot/run your Mac. The Recovery volume isn't really needed if your main volume isn't encrypted - but it's recommended to keep it.

So don't delete them! Or only delete them if you have a known good backup of your Mac!