Okay, so this is like my THIRD question today...

People that spend a lot of money on the game.... like me :'(

Whale: A creature that lives in the ocean where F2P salty tears are gathered and they thrive in it.

Jk but seriously a Whale is a name for people who spend money in the game normally whales spend atleast $1000 on the game averagely, there are also people called "Dolphins" but it does'nt make sense and is a stupid name since "dolphins" are just like whales but spend money but in "lesser" amounts.

Whales basically mean people who pour a lot of money into gacha games like Fire Emblem to try get the best characters, +10 them etc. So while F2P players will typically use units that are more common and + 10 them so they're better then the 5* exclusives whales have enough money to +10 units that are 5* exclusives and are able to sack off really rare units to make another one better.