system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why does restarting something usually fix the problem?
gpt
Problems can be caused by a number of things: A rare, randomly occurring error might overwrite some memory. Some unexpected combination of events can send something into an infinite loop or crash a critical part due to a programming error. A bit in memory may flip randomly due to pure chance, heat, or cosmic rays. Something stupid may have decided to consume all memory, grinding your system to a halt. Some programs reserve memory to do a certain task, but forget to release it again when they are done (or they don't realize that they are done). This is called a memory leak, and will slowly occupy your available memory.

When you restart a system, it forgets it's current state and initializes a new, clean, known-good state. All services are started again - whether they were crashed before or not. The data is reloaded and rebuilt in memory, no matter whether it was valid or not. Since all memory got reinitialized, the memory taken up by memory leaks is now free again, ready to be used (or slowly filled up by more leaks until you restart again).

Thus, all the effects of most random or accumulating errors are gone with a restart. Sure such an error could have broken something in a way that a restart won't fix it, but that's rare.