Ever feel like your brain is processing multiple things at once? An example might be when you’re reading a book and listening to music. While you may not realize it, your brain is processing both what you’re reading and what you’re hearing simultaneously.
A computer operates similarly; it is constantly working in the background doing multiple tasks (such as drawing the windows on your screen, checking for new e-mails, etc) all while juggling its specific user-requested tasks (such as opening a document then writing in it). The computer is doing these things concurrently just as your brain was reading a book and listening to music concurrently. It’s not sacrificing one task to complete another one; it is working on the tasks simultaneously without interruption.* This stands in contrast to processing information serially; you read a book, then you listen to music.
When we talk to another person, we expect them to understand what we’re saying because we formulate a thought, then compose our thoughts into words and finally speak those words. Likewise, a computer program generally tries to ensure the user understands what it means by handling background tasks out of sight (no windows, no warnings, etc) and only notifying the user when it is instructed to do so.
We speak with one mouth and are therefore locked to saying one thing at any given moment. That doesn’t mean we don’t make mistakes in our speech sometimes, such as by responding to the question “What would you like to eat?” with “Yes, I’d like a cheese refrigerator pizza” when we meant to say “Yes, I’d like a cheese pizza” while thinking concurrently about how we still need to fix our refrigerator. A computer can make a similar mistake when it’s instructed to tell the user “Your system is experiencing a disk space error” and “FREE VACATION – CALL NOW” simultaneously. Those two messages are unrelated and undesirable to be displayed together, let alone erroneously intertwined.
Unfortunately the bad news is that both humans and computers will likely continue to make the same mistakes for the foreseeable future. The solutions that exist for both are flawed; humans must focus extensively [not to mention consciously] to ensure only the words we wish to speak are spoken. Computers likewise must be instructed by the former (re: humans) to only output the information for which the user is meant to be provided.
The good news is that multi-threading/concurrency allows information to be processed simultaneously and therefore faster than when each action blocks subsequent actions from being processed.