What is the Apple Mercenary Attack, and Why Should You Care?

Apple rarely sends out alerts about threats, and that is because threats that target Apple devices are somewhat rare in the first place. However, on April 10, 2024, Apple saw fit to send one to certain users in 92 nations by email. These notifications were “designed to inform and assist users who may have been individually targeted by mercenary spyware attacks.” What does this mean, exactly?