When you select an answer button on a review card, Anki also applies a small amount of random “fuzz” to prevent cards that were introduced at the same time and given the same ratings from sticking together and always coming up for review on the same day.
Learning cards are also given up to 5 minutes of extra delay so that they don’t always appear in the same order, but answer buttons won’t reflect that. It is not possible to turn this feature off.
Sometimes it’s desirable to disable fuzz completely (Adding the option to disable Fuzz). Use case: learning explanation of poem parts. It’s better to have poem part1 followed by poem part2.
Other times, it’s better to increase fuzz by a big factor (More fuzz factor the further the due date). Use case: after learning a large number of cards, it’s better to distribute the review dates across separate days instead of just being overwhelmed with cards on one day.