Desiccation tolerance is like being able to survive in the desert without water for a long time. Some tiny living things, like certain seeds, can survive for many years without water because they have a special ability to protect themselves from drying out completely.
Imagine you have two plants: one is a desert plant and the other is a regular plant. Both plants need water to survive, but the desert plant can last a very long time without water. This is because inside the desert plant, there are special proteins and chemicals that help to protect its cells from drying out completely when there is no water around.
These special proteins and chemicals act like tiny umbrellas that protect the plant's cells from getting too dry. They also help the plant to store extra water, which it can use when it really needs it.
So if you think of a regular plant as a glass of water with no lid, a desert plant is like a glass of water that has a tight lid on it. The lid stops the water from evaporating, just like the special proteins and chemicals stop the water from evaporating inside the desert plant's cells.
This is why some tiny living things can survive for a long time without water even in harsh environments like deserts. They have a special ability to protect themselves from getting too dry and losing all their water.