What does "Human Mortality Plateau" mean?

Have you heard about Jeff Bezos anf Yuri Milner funding Altos labs and others over research on "IMMORTALITY".

Theories about biological limits to lifespan and evolutionary shaping of human longevity depend on facts about mortality at extreme ages. The facts have remained in dispute.

Above age 105 human mortality appears constant over age at levels that are slowly declining across cohorts.Survival to extreme ages tests the limits of evolutionary demographic potential.

we show a clean case where the plateau is real from the data of last two decades.