system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does storage on phones and computers actually work, and why is there a limit?
gpt
Modern phones and computers use "Solid State" storage. It works basically by charging super tiny parts (called floating gate transistors) in the solid state drive. These parts hold a charge, and the drive scans to see if the parts are charged (0) or not charged (1). This is binary storage, since all computers run on binary, which is just a very fast input of 1s and 0s.

You run out of storage because these transistors, small as they may be, still take up physical space. You can cram terabytes into a very small space, but this is incredibly expensive and most people don't use enough storage to make this worth it.

Some computers still use a "hard drive", which is a series of disks with small magnetic particles in them. When writing to a hard drive, a magnet sends specially timed charges to the disk, which then change the magnetic orientation of the particles, and when reading, it detects which ones are magnetized one way (1) or another way (0). Again, it's binary. A hard drive requires spinning discs so it takes a while. SSDs do not require anything moving so they are much faster.

So the even more boiled down answer: A small piece of physical space is either electrically or magnetically designated 1 or 0, which the computer can read and turn into an image on your screen. You run out of space because these small pieces are expensive to make and take up room.