Jays hide food like acorns and hazelnuts in many secret spots. Sometimes, they forget where they put their food. When they do, those acorns and nuts can start to grow into new trees. This helps the forest grow bigger and more beautiful!
Another way to say this is: Jays tuck away food in different places, but they often forget some of these spots. The acorns and hazelnuts left behind can sprout and become new trees, helping the forest get bigger.