system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is DNS cache poisoning?
gpt
So imagine you've got a massive phone book with everyone's names and phone numbers in. 

If you think you might need a particular persons number often (say, your friend 'Bob'), you might write a copy of Bobs number down on a sticky note instead of going and taking the time to find their number in the phone book each time. It saves you time and effort. This is your 'cache'.

Now imagine that your evil house mate comes along and replaces that sticky note with a different one with the same name but a different phone number. Next time you go to call Bob, you don't bother with the book and just look at the sticky note that you thought you had. Only its been tampered with, and thus you end up calling someone else. And that person you call pretends to be Bob.

Now without realising it you could be telling someone else something you only originally intended to tell Bob.