What Is A Cheatline On An Aircraft Livery?

An aircraft’s livery plays a significant role in its aesthetic appeal, adding a useful dash of variety to the photography of planespotters and aviation enthusiasts while also fostering brand recognition. Trends in liveries have come and gone over the years, and one trend that we rarely see nowadays is a cheatline. But what exactly does this refer to, and why was it such a prominent template in years gone by?