This refers to an idea in evolutionary theory which states that all species are under constant pressure to evolve into better organisms in order to survive amidst competition.
Rabbits, for instance, need to continuously evolve to run faster over time, or their population would be completely destroyed by foxes. Foxes, on the other hand, will have to constantly evolve to run faster over time, or they would be unable to hunt down rabbits that satisfy their dietary needs for survival.
The hypothesis, which is named after the Red Queen’s race in Lewis Carroll’s 1871 novel Through the Looking-Glass, was first proposed by American biologist Leigh Van Valen.