system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do computers slow down, but then you restart them and they work again?

Could you explain in the form of an analogy?  Also, has this improved over time?  Does it have anything to do with registry and defrag?  Is it different for Mac vs PC?  Thank you :)
gpt
* Think about a computer like this:
   * You are sitting at a large desk next to a huge set of bookshelves.
   * You are the CPU
   * The table is the system memory (RAM)
   * The bookshelves are the system storage (Hard Drive, SSD, external drives etc)
   * In order to do something, you need to take the related stuff off the shelf and put it on the table.
* Now think about what this table will look like as you start to do your tasks.
* Computers appear to do many things all at the same time.
* The truth is they only do one thing at a time but very very quickly switch between tasks.
* So the table gets filled with things you're working on very quickly.
* Switching between these things starts to get time consuming.
* Restarting the computer is the same as putting everything back on the shelf and totally clearing off the table.
* Those first few tasks you do will be quick because you aren't searching through a table full of stuff to get what you need.