Title text: "Sometimes, you can tell Bloom filters are the wrong tool for the job, but when they're the right one you can never be sure."
Alt text: https://explainxkcd.com/2934#Transcript
Imagine you have a lot of numbers in a set and you want a quick way to see if a number might be in the set or is definitely not in the set. A Bloom filter is a single number you OR all of the numbers in the set into so if a number might be in the set, all of its bits in the filter will be set.
Better Bloom filters involve hashing elements of the set and ORing in the hash values, but the basic idea is that the filter can only ever say if a value might be in there, with more bits allowing you to be more sure. With one bit, anything might be in there.
