Random Tick

Random ticks is a feature that updates blocks in every sub-chunk around the player. Most blocks do not respond to this, but some that have a random-ticking function implemented perform some kind of action, like growing, spreading, or decay|decaying. One of these updates is called a random tick.

The position for a random tick is calculated by choosing random blocks inside a subchunk during the chunk tick phase. The number of blocks is determined by the /gamerule random_tick_speed, a direct relationship in Java Edition when the value is the number of blocks chosen, while in Bedrock Edition it only specifies the relative speed instead of the exact number. Subchunks are 16 block vertical segments inside each chunk, with a volume of 16x16x16. If any block chosen has a random-ticking function, it will be called and the block might do something. Any block in the subchunk can be chosen, including air.

One block can also be chosen multiple times.‌[Java Edition only][verify]