when you break a lucky block something extremely bad will happen or something extremely good will happen. examples, rain creepers from the sky, rain tridents down on your head, strike tons of lightning, spawn tons of diamonds and netherite, give 5 of every spawn egg, eat the item in your hand, poor lava every were.
there is a new gamerule called one block lucky block mode which makes some tweaks to the lucky blocks such as... lucky blocks will not break when you destroy them, they will drop blocks and resources like dirt seeds sapling planks ect. there is also a new tool, the lucky breaker which breaks lucky blocks extra fast. there are also lucky potions that act like lucky blocks but without having to break a block. PS, the lucky arrow and splash potion dont work.
CHECK OUT THIS VIDEO OR YOUR LUCKY BLOCKS WILL RAIN CREEPERS
duckmasters lucky blocks video
special thx to VegaCraft check him out